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Answer 1

Implement PSL(2,3)

Since challenge to implement Galois field already have been many, I'm writing a challenge involving a group of Lie type!

Objective

Implement the multiplication and inversion in \$\text{PSL}(2,3)\$.

The ring \$\mathbb{Z}_3\$

The ring \$\mathbb{Z}_3\$ is the set \$\{0,1,2\}\$ with addition, negation, subtraction, and multiplication defined as modular arithmetic:

• Addition is the usual addition with the result moduloed by 3;

• Negation, subtraction, and multiplication are also analogously defined.

Reciprocal and division is also well-defined, but that's just another detail.

The group \$\text{SL}(2,3)\$

The multiplicative group \$\text{SL}(2,3)\$ is the set of 2-by-2 matrices whose entries are members of \$\mathbb{Z}_3\$ and the determinant is \$1\$. Note that the determinant is calculated using modular arithmetic. Matrix multiplication and matrix inversion is defined as:

• Matrix multiplication is the usual matrix multiplication, where addition and multiplication of the entries are modular;

• Matrix inversion of \$\begin{pmatrix} a & b \\ c & d \end{pmatrix}\$ is \$\begin{pmatrix} d & -b \\ -c & a \end{pmatrix}\$. This exploits that the determinant is \$1\$.

As a consequence, the elements of \$\text{SL}(2,3)\$ are:

$$\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 0 & 1 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 1 & 1 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 1 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 0 & 2\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 0 & 2\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix} $$

The factor group \$\text{PSL}(2,3)\$

\$\text{PSL}(2,3)\$ is defined as cosets of \$\text{SL}(2,3)\$ by \$\{\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}\}\$. That is, elementwise multiplications of \$\{\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}\}\$. They are: $$ \{\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 0\end{pmatrix}\}, \{\begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 2\end{pmatrix}\}, \{\begin{pmatrix} 0 & 1 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 1\end{pmatrix}\}, \{\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 0 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 2 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 0 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 1 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 1 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 0 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix}\}, \{\begin{pmatrix} 1 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 1 & 0\end{pmatrix}\}, \{\begin{pmatrix} 1 & 2 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 0 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 2 & 0\end{pmatrix}\}, \{\begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 1 & 1\end{pmatrix}\}, $$

You pick an element of each coset as representives, and don't care about the rest.

Multiplication/inversion of such representives is defined as multiplication/inversion in \$\text{SL}(2,3)\$, then taking the representive of the coset the multiplication/inversion is in. For example, \$\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}^2 = \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}\$, if \$\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}\$ and \$\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}\$ are representives.

Examples

Picking the left elements as representives of the cosets above: $$ \begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}^2 = \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}^2 = \begin{pmatrix} 1 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}\begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix} = \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}\begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix} = \begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}^{-1} = \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix} $$ To be more specific about the method of evaluation: $$ \begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}\begin{pmatrix} 0 & 1 \\ 2 & 2\end{pmatrix} ≡ \begin{pmatrix} 2 & 2 \\ 2 & 4\end{pmatrix} ≡ \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix} ≡ \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \\ \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}^{-1} ≡ \begin{pmatrix} 2 & -1 \\ -1 & 1\end{pmatrix} ≡ \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix} ≡ \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix} $$ The steps of this algorithm is:

1. Do usual matrix multiplication/inversion;
2. Modulo the entries by 3;
3. Take the representive of the coset.

Though you can make any possible algorithm.

Rules

• Input type and format doesn't matter, but it must be a container of integers. In C, int[2][2] and int[4] are valid examples. This restriction prevents abusing the fact that \$\text{PSL}(2,3) \cong A_4\$.
• Output type and format doesn't matter either, but it must be the same as the input type and format.
• Invalid inputs fall in don't care situation.
• Multiplication and inversion may be in separate codes. In this case, the score is the sum of their lengths in bytes.
• Since this is a code-golf, the code with least score wins.

Answer 2

Very rough outline of a challenge that rewards short programs that take a long time.

Probably a no input and output can be anything except an error challenge.

Is there a nice way to exclude things like sleep(), wait() etc?

Would be required for 1 person to run all the programs for the timing to be fair.

Thinking that answers would include loops, recursion, testing of complex criteria.

Answer 3

Design a Stack With Increment Operation

Design a stack that supports the following operations.

Implement the CustomStack class:

• CustomStack(int maxSize) Initializes the object with maxSize which is the maximum number of elements in the stack or do nothing if the stack reached the maxSize.
• void push(int x) Adds x to the top of the stack if the stack hasn't reached the maxSize.
• int pop() Pops and returns the top of stack or -1 if the stack is empty.
• void inc(int k, int val) Increments the bottom k elements of the stack by val. If there are less than k elements in the stack, just increment all the elements in the stack.

Test Case:

Input

["CustomStack","push","push","pop","push","push","push","increment","increment","pop","pop","pop","pop"]
[[3],[1],[2],[],[2],[3],[4],[5,100],[2,100],[],[],[],[]]


Output

[null,null,null,2,null,null,null,null,null,103,202,201,-1]

Explanation


CustomStack customStack = new CustomStack(3); // Stack is Empty []
customStack.push(1);                          // stack becomes [1]
customStack.push(2);                          // stack becomes [1, 2]
customStack.pop();                            // return 2 --> Return top of the stack 2, stack becomes [1]
customStack.push(2);                          // stack becomes [1, 2]
customStack.push(3);                          // stack becomes [1, 2, 3]
customStack.push(4);                          // stack still [1, 2, 3], Don't add another elements as size is 4
customStack.increment(5, 100);                // stack becomes [101, 102, 103]
customStack.increment(2, 100);                // stack becomes [201, 202, 103]
customStack.pop();                            // return 103 --> Return top of the stack 103, stack becomes [201, 202]
customStack.pop();                            // return 202 --> Return top of the stack 102, stack becomes [201]
customStack.pop();                            // return 201 --> Return top of the stack 101, stack becomes []
customStack.pop();                            // return -1 --> Stack is empty return -1.

This is code-golf so shortest submission in bytes wins! If you liked this challenge, consider upvoting it... And happy golfing!

Answer 4

Find the longest common subsequence

Given two integer arrays. Find the longest common subsequence

Test Case:

Input:

a=[1,5,2,6,3,7]
b=[5,6,7,1,2,3]

Output:

Return
[1,2,3] or [5,6,7]

This is code-golf so shortest submission in bytes wins! If you liked this challenge, consider upvoting it... And happy golfing!

Answer 5

The (All But) Quine challenge

Like a quine challenge, but the opposite. Print everything except source code

Challenge

Write a program, which takes no input, and outputs all the strings of printable characters which are the same length as the source code of the program, except the source code of the program.

Scoring

The shortest program (per language) to accomplish the above task, wins

Answer 6

Maximum Performance of a Team

There are \$n\$ engineers numbered from 1 to \$n\$ and two arrays: speed and efficiency, where \$speed[i]\$ and \$efficiency[i]\$ represent the speed and efficiency for the i-th engineer respectively. Return the maximum performance of a team composed of at most \$k\$ engineers, since the answer can be a huge number, return this modulo \$10^9 + 7.\$

The performance of a team is the sum of their engineers' speeds multiplied by the minimum efficiency among their engineers.

Test Case 1:

Input: n = 6, speed = [2,10,3,1,5,8], efficiency = [5,4,3,9,7,2], k = 2

Output: 60

Explanation:

We have the maximum performance of the team by selecting engineer 2 (with speed=10 and efficiency=4) and engineer 5 (with speed=5 and efficiency=7). That is, performance = \$(10 + 5) * min(4, 7) = 60.\$

Test Case 2:

Input: n = 6, speed = [2,10,3,1,5,8], efficiency = [5,4,3,9,7,2], k = 3

Output: 68

Explanation:

This is the same example as the first but k = 3. We can select engineer 1, engineer 2 and engineer 5 to get the maximum performance of the team. That is, performance = \$(2 + 10 + 5) * min(5, 4, 7) = 68.\$

Test Case 3:

Input: n = 6, speed = [2,10,3,1,5,8], efficiency = [5,4,3,9,7,2], k = 4

Output: 72

Please feel free to add more test cases.

This is code-golf so shortest submission in bytes wins! If you liked this challenge, consider upvoting it... And happy golfing!

Answer 7

Numbers by index

Challenge

Print the numbers:

0
1
22
333
4444
55555
666666
7777777
88888888
999999999

In that order.

I/O

Takes no input. The numbers can have any delimiters desired (or none). Example outputs:

0122333444455555666666777777788888888999999999

[0,1,22,333,4444,55555,666666,7777777,88888888,999999999]

etc....

Code Example

This is an un-golfed example that may perhaps act as algorithm guide (or maybe not):

Turing Machine Code, 553 bytes

0 * 0 r K
K * _ r 1
1 * 1 r L
L * _ r 2
2 * 2 r a
a * 2 r M
M * _ r 3
3 * 3 r b
b * 3 r c
c * 3 r N
N * _ r 4
4 * 4 r d
d * 4 r e
e * 4 r f
f * 4 r O
O * _ r 5
5 * 5 r g
g * 5 r h
h * 5 r i 
i * 5 r j
j * 5 r P
P * _ r 6
6 * 6 r k
k * 6 r l
l * 6 r m
m * 6 r n
n * 6 r o
o * 6 r Q
Q * _ r 7
7 * 7 r p
p * 7 r q
q * 7 r r
r * 7 r s
s * 7 r t
t * 7 r u
u * 7 r R
R * _ r 8
8 * 8 r v
v * 8 r w
w * 8 r x
x * 8 r y
y * 8 r z
z * 8 r A
A * 8 r B
B * 8 r S
S * _ r 9
9 * 9 r C
C * 9 r D
D * 9 r E
E * 9 r F
F * 9 r G
G * 9 r H
H * 9 r I
I * 9 r J
J * 9 r halt

Try it online!

This prints out the numbers with a space delimiter:

0 1 22 333 4444 55555 666666 7777777 88888888 999999999

Challenge Type

code-golf, so shortest answer in bytes (by language) wins.

Edit: Link to the related challenge. Curiously, there is one answer on there where if it was by index, and the zero was included, it would be shorter.

Answer 8

A malbolge interpreter

The challenge today is to write a Malbolge interpreter.

Specification

Malbolge
'98, Ben Olmstead

I hereby relenquish any and all copyright on this language,
documentation, and interpreter; Malbolge is officially public domain.

------------------------------------------------------------------------

                                Malbolge
                           '98, Ben Olmstead

Introduction
^^^^^^^^^^^^

It was noticed that, in the field of esoteric programming languages,
there was a particular and surprising void: no programming language
known to the author was specifically designed to be difficult to program
in.

Certainly, there were languages which were difficult to write in, and
far more were difficult to read (see: Befunge, False, TWDL, RUBE...).
But even INTERCAL and BrainF***, the two kings of mental torment, were
designed with other goals: INTERCAL to have nothing in common with any
major programming language, and BrainF*** to be a very tiny, yet still
Turing-complete, language.

INTERCAL's constructs are certainly tortuous, but they are all too
flexible; you can, for instance, quite easily assign any number to a
variable with a single statement.

BrainF*** is lacking the flexibility which is INTERCAL's major weakness,
but it fails in that its constructs are far, far too intuitive.
Certainly, there are only 8 instructions, none of which take any
arguments--but it is quite easy to determine how to use those
instructions.  Subtract 8 from the current number?  With a simple
'--------' you are done!  This kind of simple answer was unacceptable to
the author.

Hence the author created Malbolge.  It borrows from machine, BrainF***,
and tri-INTERCAL, but put together in a unique way.  It was designed to
be difficult to use, and so it is.  It is designed to be
incomprehensible, and so it is.

So far, no Malbolge programs have been written.  Thus, we cannot give an
example.

"Malbolge" is the name of Dante's Eighth Circle of Hell, in which
practitioners of deception (seducers, flatterers, simonists, thieves,
hypocrites, and so on) spend eternity.


Environment
^^^^^^^^^^^

In many languages, the environment is easy to understand.  In Malbolge,
it is best to understand the runtime environment before you ever see a
command.

The environment is, roughly, that of a primitive trinary CPU.  Both code
and data share the same space (the machine's memory segment), and there
are three registers.  Machine words are ten trits (trinary digits) wide,
giving a maximum possible value of 59048 (all numbers are unsigned).
Memory space is exactly 59049 words long.

The three registers are A, C, and D.  A is the accumulator, used for
data manipulation.  A is implicitly set to the value written by all
write operations on memory.  (Standard I/O, a distinctly non-chip-level
feature, is done directly with the A register.)

C is the code pointer.  It is automatically incremented after each
instruction, and points the instruction being executed.

D is the data pointer.  It, too, is automatically incremented after each
instruction, but the location it points to is used for the data
manipulation commands.

All registers begin with the value 0.

When the interpreter loads the program, it ignores all whitespace.  If
it encounters anything that is not one of an instruction and is not
whitespace, it will give an error, otherwise it loads the file, one non-
whitespace character per cell, into memory.  Cells which are not
initialized are set by performing op on the previous two cells
repetitively.


Commands
^^^^^^^^

When the interpreter tries to execute a program, it first checks to
see if the current instruction is a graphical ASCII character (33
through 126).  If it is, it subtracts 33 from it, adds C to it, mods it
by 94, then uses the result as an index into the following table of 94
characters:

            +b(29e*j1VMEKLyC})8&m#~W>qxdRp0wkrUo[D7,XTcA"lI
            .v%{gJh4G\-=O@5`_3i<?Z';FNQuY]szf$!BS/|t:Pn6^Ha

It then checks it against the characters listed below, and performs an
appropriate action.

If the result is not one of the characters listed below, it is treated
as a nop.  If the original character is not graphic ASCII, the program
is immediately ended.

When the interpreter parses the input file, it checks each non-
whitespace character with the process above.  If any result is not one
of the eight characters below, the file will be rejected.

After the instruction is executed, 33 is subtracted from the instruction
at C, and the result is used as an index in the table below.  The new
character is then placed at C, and then C is incremented.

            5z]&gqtyfr$(we4{WP)H-Zn,[%\3dL+Q;>U!pJS72FhOA1C
            B6v^=I_0/8|jsb9m<.TVac`uY*MK'X~xDl}REokN:#?G"i@

j
  sets the data pointer to the value in the cell pointed to by the
  current data pointer.

i
  sets the code pointer to the value in the cell pointed to be the
  current data pointer.

*
  rotates the trinary value of the cell pointed to by D to the right 1.
  The least significant trit becomes the most significant trit, and all
  others move one position to the left.

p
  performs a tritwise "op" on the value pointed to by D with the
  contents of A.  The op (don't look for pattern, it's not there) is:

            | A trit:
    ________|_0__1__2_
          0 | 1  0  0
      *D  1 | 1  0  2
     trit 2 | 2  2  1



Di-trits:
    00 01 02 10 11 12 20 21 22

00  04 03 03 01 00 00 01 00 00
01  04 03 05 01 00 02 01 00 02
02  05 05 04 02 02 01 02 02 01
10  04 03 03 01 00 00 07 06 06
11  04 03 05 01 00 02 07 06 08
12  05 05 04 02 02 01 08 08 07
20  07 06 06 07 06 06 04 03 03
21  07 06 08 07 06 08 04 03 05
22  08 08 07 08 08 07 05 05 04

<
  reads an ASCII value from the stdin and converts it to Trinary, then
  stores it in A.  10 (line feed) is considered 'newline', and
  2222222222t (59048 dec.) is EOF.

/
  converts the value in A to ASCII and writes it to stdout.  Writing
  10 is a newline.

v
  indicates a full stop for the machine.

o
  does nothing, except increment C and D, as all other instructions do.


Turing-Completeness
^^^^^^^^^^^^^^^^^^^

Though I have not proven it, I _think_ Malbolge to be Turing-complete.
To be Turing-complete, there must be some data construct which can be
used to do any mathematical calculation.  I believe that using *p in
various clever ways on the tritwords can fulfill this requirement.

Turing-completeness also requires three code constructs: sequential
execution (which Malbolge obviously has), repetition (provided by the
i and, indirectly, j instructions), and conditional-execution (provided,
I believe, by self-modifying code and altering i destinations).

I do have my doubts, particularly about data constructs, but I *think*
this works...


Appendix: Trinary Conversion Table
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Trinary to ASCII to decimal to hex table, provided, strangely enough,
for the convenience of Malbolge programmers.

00000 NUL 000 00    01012   032 20    02101 @ 064 40    10120 ` 096 60
00001 SOH 001 01    01020 ! 033 21    02102 A 065 41    10121 a 097 61
00002 STX 002 02    01021 " 034 22    02110 B 066 42    10122 b 098 62
00010 ETX 003 03    01022 # 035 23    02111 C 067 43    10200 c 099 63
00011 EOT 004 04    01100 $ 036 24    02112 D 068 44    10201 d 100 64
00012 ENQ 005 05    01101 % 037 25    02120 E 069 45    10202 e 101 65
00020 ACK 006 06    01102 & 038 26    02121 F 070 46    10210 f 102 66
00021 BEL 007 07    01110 ' 039 27    02122 G 071 47    10211 g 103 67
00022 BS  008 08    01111 ( 040 28    02200 H 072 48    10212 h 104 68
00100 HT  009 09    01112 ) 041 29    02201 I 073 49    10220 i 105 69
00101 LF  010 0a    01120 * 042 2a    02202 J 074 4a    10221 j 106 6a
00102 VT  011 0b    01121 + 043 2b    02210 K 075 4b    10222 k 107 6b
00110 FF  012 0c    01122 , 044 2c    02211 L 076 4c    11000 l 108 6c
00111 CR  013 0d    01200 - 045 2d    02212 M 077 4d    11001 m 109 6d
00112 SO  014 0e    01201 . 046 2e    02220 N 078 4e    11002 n 110 6e
00120 SI  015 0f    01202 / 047 2f    02221 O 079 4f    11010 o 111 6f
00121 DLE 016 10    01210 0 048 30    02222 P 080 50    11011 p 112 70
00122 DC1 017 11    01211 1 049 31    10000 Q 081 51    11012 q 113 71
00200 DC2 018 12    01212 2 050 32    10001 R 082 52    11020 r 114 72
00201 DC3 019 13    01220 3 051 33    10002 S 083 53    11021 s 115 73
00202 DC4 020 14    01221 4 052 34    10010 T 084 54    11022 t 116 74
00210 NAK 021 15    01222 5 053 35    10011 U 085 55    11100 u 117 75
00211 SYN 022 16    02000 6 054 36    10012 V 086 56    11101 v 118 76
00212 ETB 023 17    02001 7 055 37    10020 W 087 57    11102 w 119 77
00220 CAN 024 18    02002 8 056 38    10021 X 088 58    11110 x 120 78
00221 EM  025 19    02010 9 057 39    10022 Y 089 59    11111 y 121 79
00222 SUB 026 1a    02011 : 058 3a    10100 Z 090 5a    11112 z 122 7a
01000 ESC 027 1b    02012 ; 059 3b    10101 [ 091 5b    11120 { 123 7b
01001 FS  028 1c    02020 < 060 3c    10102 \ 092 5c    11121 | 124 7c
01002 GS  029 1d    02021 = 061 3d    10110 ] 093 5d    11122 } 125 7d
01010 RS  030 1e    02022 > 062 3e    10111 ^ 094 5e    11200 ~ 126 7e
01011 US  031 1f    02100 ? 063 3f    10112 _ 095 5f

11202 128 80    12221 160 a0    21010 192 c0    22022 224 e0
11210 129 81    12222 161 a1    21011 193 c1    22100 225 e1
11211 130 82    20000 162 a2    21012 194 c2    22101 226 e2
11212 131 83    20001 163 a3    21020 195 c3    22102 227 e3
11220 132 84    20002 164 a4    21021 196 c4    22110 228 e4
11221 133 85    20010 165 a5    21022 197 c5    22111 229 e5
11222 134 86    20011 166 a6    21100 198 c6    22112 230 e6
12000 135 87    20012 167 a7    21101 199 c7    22120 231 e7
12001 136 88    20020 168 a8    21102 200 c8    22121 232 e8
12002 137 89    20021 169 a9    21110 201 c9    22122 233 e9
12010 138 8a    20022 170 aa    21111 202 ca    22200 234 ea
12011 139 8b    20100 171 ab    21112 203 cb    22201 235 eb
12012 140 8c    20101 172 ac    21120 204 cc    22202 236 ec
12020 141 8d    20102 173 ad    21121 205 cd    22210 237 ed
12021 142 8e    20110 174 ae    21122 206 ce    22211 238 ee
12022 143 8f    20111 175 af    21200 207 cf    22212 239 ef
12100 144 90    20112 176 b0    21201 208 d0    22220 240 f0
12101 145 91    20120 177 b1    21202 209 d1    22221 241 f1
12102 146 92    20121 178 b2    21210 210 d2    22222 242 f2
12110 147 93    20122 179 b3    21211 211 d3
12111 148 94    20200 180 b4    21212 212 d4
12112 149 95    20201 181 b5    21220 213 d5
12120 150 96    20202 182 b6    21221 214 d6
12121 151 97    20210 183 b7    21222 215 d7
12122 152 98    20211 184 b8    22000 216 d8
12200 153 99    20212 185 b9    22001 217 d9
12201 154 9a    20220 186 ba    22002 218 da
12202 155 9b    20221 187 bb    22010 219 db
12210 156 9c    20222 188 bc    22011 220 dc
12211 157 9d    21000 189 bd    22012 221 dd
12212 158 9e    21001 190 be    22020 222 de
12220 159 9f    21002 191 bf    22021 223 df

Notes

Note that the original specification has one quirk: after encountering an illegal instruction, the interpreter hangs. You may choose which behaviour do you want to implement (hang or exit).

I/O rules

The program or function has to take input in any reasonable way (for the program), and somehow supply the input and output features to the malbolge program (either by return value / parameter, tty or a file).

Sandbox stuff

note: I'm a bit unsure about the scoring criterion: would popularity-contest be good? I'm mostly looking for creative answers

Answer 9

Write two programs (likely functions since IO for float convert to/from stream, losing info as mentioned later), one given \$n\geq 2\$ real points on a 2D plane, returning \$2n-3\$ real numbers; another given the \$2n-3\$ real numbers, return the same shape and size given to first program. Order of points matters. Returning a mirrored shape is fine.

You must use an in-language float and assume it is infinitely precise, but converting to types like string or trying to handle the bits in RAM truncate the precision. There's no requirements on how you map, so you can even just pack some real numbers into one if your language happens to have way to do that.

code-golf

Answer 10

What day is it today? atomic-code-golf

Given a date y4y3y2y1-m2m1-d2d1, output the day in the week w. 0 as Sunday, 1 as Monday, and so on. You can assume the date is valid, and we use the current date rule and leap rule.

Each submission should be written in this specific programming language:

• A program consists of a mapping from string of digits to digits, and a sequence of instructions.
• Each instruction has the format: var=[var|dgt],[var|dgt],...,[var|dgt], which assigns the value of looking up the string constructed by concatenating the values of the right hand side elements ([var|dgt],[var|dgt],...,[var|dgt]) together in the table and put it into the var on the left.

A program is valid if:

• None of the lookup step fails for all valid input date.
• Given any valid date in the format mentioned above (initially assigned to the 8 variables y4 y3 y2 y1 m2 m1 d2 d1), after the program is run, the correct result is assigned to the variable w.

You can create as many variables as you like(though bounded by amount of instructions), each variable only containing a digit.

Solution win if there's no strictly better solution, aka. no solution that take less or same amount of items in mapping table, less or same amount of instrucions, and at least one of amounts of items and instructions is less.

For example, this is a solution that wins:

3652425 items 1 instruction

003000101 -> 6
003000102 -> 0
003000103 -> 1
...
993991231 -> 5
-------------
w=y4,y3,3,y2,y1,m2,m1,d2,d1

Here, the 3 on 3rd position can be used without any extra cost. This can be used to create multiple mappings, and sometimes save elements when there are more mapping instructions.

A checker is provided here.

Answer 11

Natural Language Identification Using Only Regular Expressions

code-golf sandbox winning-criteria discussion

For example:

const regex = /English(?=\w+ Hello World)|Spanish(?= Hola Mundo)/;

console.log('EnglishSpanish Hello World'.match(regex)); // English
console.log('EnglishSpanish Hola Mundo'.match(regex)); // Spanish

These wordlists are to be used, and words are to be rewritten entirely using the ASCII characters A-Z and a-z. Languages which use characters that cannot be easily transcribed into ASCII without special knowledge or firsthand experience in that language, are excluded.

For instance, the Albanian word të is easily transcribed without special knowledge as te, so Albanian is allowed.

But the Arabic word من cannot be, so Arabic is excluded.

The regular expression must match the language exactly, so appending a list of all languages you are testing before each word is allowed. But however you organize this list, it must be the same for every word you test. See the example above for clarification.

Sandbox Questions

Ideally, brevity of regex, accuracy of language identification, and number of languages taken into account by the regex should all be considered when determining the winner. But I have not decided on that yet, and am very open to suggestions.

In fact this is my first sandbox post and I hope someone can help me format this properly with good rules so that it makes for an interesting and fun challenge. I got this idea from some other contest somewhere where the goal was to identify languages with at least 60% accuracy. But I can't find it anymore.

Answer 12

Char tetris code-golf

** NOTE** After a while I didn't get any insights, but after thinking a bit about this I realized it can't be deterministic because different approaches may produce different results. I think this is not appropriate for a competition so I keep holding this until I find a solution, hoping someone can give advices.

This tetris has characters instead of shapes.

The task is similar to a normal tertris game: you have to fit blocks to keep it down.

The difference is that we use the bits of every ascii codepoint instead of shapes.

. Rules

Blocks are placed only orizontally.

You can move blocks left or right.

You can rotate the bits by 180 degrees(invert).

The field is 16 bit wide.

Trailing or leading zeros can go outside the field.

Ones cannot go outside the field.

If all the ones of the block fits into the 0s of the top line the block falls trough, if the same happens on the next level (also moving it) it falls again.

When you have 8 bits with value 1 next to each other orizontally the entire line is cleared and the other lines falls.

You place those blocks following the sequence.

While placing a block your program has to take care only of the current block.

. input
A sequence of printable ascii characters

. output
The resulting height reached after all the blocks are used, obviously your program must output the shortest height.

Answer 13

Create a Drawing Guide for a Polygram

Poor old Jim, he's just terrible at drawing polygrams, and he's asked you to create a "drawing guide" for him - an ascii polygram with numbered edges, so he can follow the instructions.

Challenge

Write a program to produce an ascii polygram with P <= 10; each edge of the polygram should be made of a single digit 0-9, showing the order in which the edges should be drawn.

Input

Your program should receive (via STDIN, as function arguments, or some other language-appropriate method): P, the number of edges/vertices of the polygram, and Q, the spacing. In the notation as per the Wikipedia link, you'll be drawing a {p/q} polygram.

Output

Either print to STDOUT or return (or something else language-appropriate) a multiline string showing the drawing guide for the given polygram. The string can be any size you like, as long as it's large enough to display a clear polygram.

Notes

Your code should be able to handle compound regular polygons as well as regular regular polygons, and also inputs of q > p/2 (poor old Jim doesn't realize that the polygram for {p/q} is the same as for {p/p-q}).

Example Output for {10,3}

              5              
             5 4             
                4            
     21     5        888     
     2 11115     8888  7     
     2    5111888 4    7     
     2     888111  4   7     
     2  888      111   7     
     8885           4117     
  8882               4 711   
 8   2 5               7  111
     25               47     
 9   5                 7    0
  9  2                 74  0 
    52                 7  0  
   9 2                 7 4   
  5 92                 7 04  
     9                 70  4 
 5   2                 7     
5    29                7    4
6666 2 9              07   33
    666              0 7333  
     2 696           337     
     2   9666     333  7     
     2    9  66633 0   7     
     2      333 666    7     
     2   339       666 7     
     2333   9    0    67     
             9  0            
               0 

Scoring

This is code-golf, so shortest in bytes wins. Tiebreaker goes to the most votes.

Answer 14

Pointer to pointers to pointers to pointers

You should choose a language supporting pointers like C. And your task is simple: demonstrate a legitimate use of the most level of pointers.

You should justify your code by describing an algorithm that:

• Has only plain text, number or an array of those as input and output.
• You think it will make things easier to write those code as a part of the implementation of this algorithm.
• This implementation would have optimum memory usage (only declared variables and parameters, explicitly allocated space, and the return addresses for recursive functions count).

Other rules:

• They must be pointers to pointers directly, i.e. a pointer to an object containing a pointer doesn't count. It's better if nobody using this code will want to extend some pointer to an object later.
• Each pointer must have a different type (if your language can somehow make them the same type).
• You should create at least one pointer, and either dereference or compare two non-null pointers once in each level.
• Using pointers as arrays is only half as interesting.
• Iterators, etc, are considered in essence pointers and allowed in this challenge. But you can't define new types implementing iterators for this purpose.

popularity-contest

Answer 15

Winning Tic-Tac-Toe lines

fastest-code

For a given tic-tac-toe board of size N**D (for example, a normal tic-tac-toe game is 3**2), the number of winning lines of length N is given by the expression:

$$ 2^{D-1} + \sum_{S=1}^{D-1}2^{S-1}DN^{D-S} $$

(Basically, you are summing the number of lines in each S-dimensional slice of the board.)

The challenge:

Given N and D, your answer should output a list of D-dimensional coordinates for each winning line. Input and output are any reasonable format. You can assume that both N and D are positive integers, with N > 1. (Degenerate cases of N=1, D>1 not included.)

Since this is fastest-code, fastest answer wins. Please explain your algorithm!

Answer 16

Ayn Random number generator

---

Inspired by xkcd 1277:

Write a random number generator that takes no input and generates a random integer between 1 and 100. When run less than 200 times, the frequency of all numbers needs to be between 0 and 2, but when it's ran 50 000 times, the number 42 (obviously) should have a frequence that's more than 4 standard deviations higher than the mean.

Format is code-golf. Your score is the bytecount of your code.

Answer 17

Please nitpick this. If there's anything that wouldn't work or would be inconvenient, however small of an issue it is, tell me about it!
Also, suggestions for [adjective] are more than welcome.

---

Determine how [adjective] a number is (code-golf)

A number would be considered [adjective] if 0 is the result of multiplying its digits together, then multiplying the digits of the resulting number, then repeating until a single-digit number is produced. The more steps it takes to reach 0, the more [adjective] the number is; if the resulting number is not 0, though, the number is not [adjective] regardless of how long it took to finish.
The formula used to determine [adjective]-ness is 10-10/T where T is however many numbers it took to reach 0 (including 0 and the initial input)

Your goal is, as the title says, to write a program or function that determines how [adjective] a number is, and prints every iteration along the way. Here are some example inputs/ouputs:

in: 879
out: 879    <-       (T=1)
     504    <- 8*7*9 (T=2)
     0      <- 5*0*4 (T=3)
            <- optional newline
     6.6... <- 10-10/3 (repeating decimals can be expressed in any way you want)

in: 2468
out: 2468   <-  T=1
     96     <- (T=2) 2*4*6*8
     54     <- (T=3) 9*6
     20     <- (T=4) 5*4
     0      <- (T=5) 2*0

     8      <- 10-10/5

in: -888
out: -888  
     -512   <- -8*-8*-8
     -10    <- -5*-1*-2
     0      <- -1*0

     6.6... <- 10-10/3

in: 1344
out: 1344
     48
     32
     6

     0    <- did not produce 0, so the prog/func returns 0

Your program must follow these rules:

-Takes input from STDIN.
-Throws an "error" (printed to STDOUT) and halts immediately after input if the input has one or more 0s in it or if it's less than three digits in length. The error must be a string, and as it's supposed to be printed to stdout, cannot be one generated by the language itself (eg 1/int(min(input())) to check if it's zero). Lastly, the error message has to clearly define what the error is; ERR:0 and ERR:LEN, for example, would suffice.

Bonuses/Penalties:

-25 if it properly handles decimals. For instance, an input of 99.22 would first turn into 9*9 + 0.(2*2), or 9*9 + 0.4, and so on.

---

This is code-golf, so the shortest answer in bytes wins.

Answer 18

Represent a Number in the Strangest Way You Can Think Of.. while staying under 8 unique characters

Your goal is to represent some numbers in the strangest way possible.

Rules:

• The result must be a number that can be used in the programming language like any other ordinary number. For instance, <my expression> + 3 should return 3 more than the value of <my expression>.
• The code must be under 20 kilobytes. That's a rather large size for a number so you should be all set.
• The expression must have under 8 unique characters! The length of it can be as long you want, just keep it under 8 unique characters. aaaaaaaaaaaaaaaaaa is valid (if it works in the programming language) but abcdefghijklm isn't valid because it uses 8 or more unique characters.

Guidelines:

• The goal here is to represent a number in the strangest and most interesting way possible, so if I ask you to represent the number 35 it would be a good idea to respond with something more interesting than 35 or 12 + 23.
• This isn't a code-golf! Feel free to make your code as long as you want, so long as it's under 20 kilobytes. Fancy code can look nice!
• The code doesn't need to support decimals (floats) but if it does, it will get 10 extra points (see below).
• The code also doesn't need to support negative numbers (for instance -37) but if it does, it will get 10 extra points (see below).
• Try to make your post follow the below:

Post format:

Language

Description

0

...

1

...

30

...

108

...

1337

...

1234567890

...

3.1415 [10 bonus points if you can get this!]

...

-25 [10 bonus points if you can get this!]

...

Bonus numbers:

...

The points is equivalent to the number of votes on the answer plus 10 if it supports decimals with 10 more points if it supports negative numbers. Whoever has the highest points is considered the current winner. Have fun!

---

This is my first go at making a popularity contest so if you have any tips those would be appreciated.. :)

Answer 19

Wrong tool for the task

code-golf code-bowling cops-and-robbers math

Task

Write two full programs in the same programming language that solve the following two tasks:

1. Read two positive integers from STDIN and print their sum to STDOUT.

2. Read two positive integers from STDIN and print their product to STDOUT.

Additional details:

• Given enough time and memory, your programs has to support arbitrarily large integers.

• All integers (input and output) use standard decimal notation, have no leading zeroes and are followed by a single linefeed.

Scoring

The first task is code golf, so your objective is to make your program as short as possible.

The second task is code bowling, so your objective is to make your program as long as possible.

Your score is defined as follows:

The highest score wins!

Robbing a language

There's a catch! Only the submission with the shortest program in a particular language will be considered valid for task 2, so there can only be one valid answer per language.

This means that you cannot deliberately write a huge program for task 2; you actually have to pick the "wrong tool" for the task.

Additional details:

• Task 1 exists merely to provide the proper denominator for the score (and robbers have no moral anyway), so byte-per-byte copies of somebody's program for task 1 are allowed.

• If two answers use the same language and have programs of the same length for task 2, the answer that achieved that length first will be considered valid.

• If somebody invalidated your answer, you may attempt to golf your answer to revalidate yours and invalidate his.

Answer 20

GitHub Gist command-line client

Create a command-line tool that publishes a list of files as one public GitHub Gist.

Specification

The following bullet points describe the behavior of the program. If a bullet point has "must", you must implement that point. If a bullet point has "can optionally" or "should optionally" you can implement that point on your own volition.

1. It must be a complete command-line program.
2. It must use the GitHub Gists API.
3. It must post an anonymous Gist (that is, not as a GitHub user).
4. Gisted files must use the filename provided on the command-line.
5. The command-line must accept multiple positional arguments.
6. If no arguments are specified, it must print this usage to STDOUT: gist: usage: <file> [file...] verbatim then exit with code 0.
7. If something else goes wrong, it must print this message to STDERR: gist: unable to gist =( verbatim then exit with code 1.
8. If everything is successful it must print the Gist's HTML URL to STDOUT.
9. It can optionally accept a flag for description -d <description. floor(score * .9)
10. It can optionally accept a flag for private gisting -p. floor(score * .9)
11. In the case that a description flag is not used or implemented it must set the description to an empty string.

Example Input/Output

The number before the prompt is the exit code of the previous command.

0 $ gist
gist: usage: <file> [file...]
0 $ gist no-such-file.txt
gist: unable to gist =(
1 $ gist hello.txt
https://gist.github.com/anonymous/1e645596ce7bceeb1ec9
0 $

Scoring

This is a code-golf so shortest answer wins. As stated above, the following multipliers are in effect:

• (9): score = floor(score * .9)
• (10): score = floor(score * .9)
• Both (9) & (10): score = floor(floor(score * .9) *.9)

Answer 21

Golf these arrays

Your task is to output these 128 arrays: http://pastebin.com/UeBMJfv7

Gzip base64: (too long, will be added if I'll post this question).

Rules

• You don't have to output them all. And you can output the arrays in any order. But the order of items in the arrays must be kept as is.
• You can print other arrays, which wouldn't be counted towards your score. The number of arrays you print must be no more than 10,000, and the total number of arrays, subarrays and numbers must be no more than 10,000,000.
• You can use any convenient format to represent the arrays (and the list of outputted arrays).

Scoring

If your program or function has n bytes, and it printed k distinct arrays from the above list, your score would be n*(128/k)². Lowest score wins.

---

Problems

It looks too boring.

Answer 22

The Perfect Keyboard

Back in the 1970s, keyboard designers respected the needs of programmers and languages. For example, see the IBM 2741 keyboard, designed for APL (from Wikipedia):

Today, sadly, most code golfers are forced to struggle with standard keyboards, which are badly suited to the needs of their language. This has to change!

The challenge

1. Choose a programming language.
2. Design a keyboard, which would best suit the needs of a developer (or specifically a code golfer) in said language.
3. Post the keyboard layout as an answer.
4. Explain how your keyboard enhances the programming experience.
5. Start counting votes for 7 days, until I acceopt the winning answer (the answer with most votes).
6. Optional - if you are the winner, start a Kickstarter project to build the thing.

Expected Answers

This section is, of course, for the sandbox only.

I don't really expect a keyboard design which would actually improve functionality of programs in an actual serious language. I'd expect fun answers, where the keyboard design highlights soemthing fun/interesting/absurd about the language. But my expectations don't matter so much, because it's not me rating the answers, but the other users.

Example (not very good ones):

1. A Brainfuck keyboard with only 4 keys.
2. A Lisp keyboard where half the keys are parentheses.
3. A Piet keyboard - I'm sure someone will come up with something nice.

popularity-contest

Answer 23

Technologic - Now what's THAT command do??

Daft Punk's song "Technologic" is all about actions that a user or computer does when it's working and being used. You goal is to write a program that has one command we will call the Technologic Command. This command will executes all of the actions like "buy it", "lock it", "code it", and "write it" in the order the lyrics are written on 'it'. What 'it' is is up to you, but you gotta let me know.

Rules

• Any language can be used.
• The song refers to an 'it'. That can be a block a memory, algorithm, function, file, or anything else a computer can manipulate directly or indirectly.
• You must specify what 'it' is you will be performing these actions on. If you don't, you can only earn a maximum of 160 points.
• Points will be deducted otherwise if a command is not used.
• I'm not aware of any 'buy' command, method, function, subroutine or instruction so use a thesaurus and find the closest word you can actually program. I don't expect the program to actually buy or snap anything. Other words like mail and fax are possible, but not recommended.
• If you have to use a synonym, you are not allowed to use that command again
• Encompassing multiple objects into one artifact does not count. For example, taking the command "name it" literally means you won't be able to name an array of bytes, but you can name a file. Creating an object that holds both a file and an array of bytes is not allowed. That would make this too easy to get the maximum amount of points.

Scoring

• There are 16 commands with a total possible score of 190 points.
• 10 points for executing a command on the specified 'it' of your choosing (160 total)
• 2 points for executing each command consecutively that references your 'it' (30 total)
• 5 points for executing a command on something other than your 'it'
• -3 points for every command skipped.

Command List

lyrics

Buy it, use it, break it, fix it,
Trash it, change it, mail - upgrade it,
Charge it, point it, zoom it, press it,
Snap it, work it, quick - erase it,
Write it, cut it, paste it, save it,
Load it, check it, quick - rewrite it,
Plug it, play it, burn it, rip it,
Drag and drop it, zip - unzip it,
Lock it, fill it, call it, find it,
View it, code it, jam - unlock it,
Surf it, scroll it, pause it, click it,
Cross it, crack it, switch - update it,
Name it, rate it, tune it, print it,
Scan it, send it, fax - rename it,
Touch it, bring it, pay it, watch it,
Turn it, leave it, start - format it.

code-challangesequence

Answer 24

Just Golf 2016 code-golf kolmogorov-complexity

(Related: A Kingdom Hearts VGM challenge) Sandbox note: potential duplicate?

Just Dance 2016 is coming out soon, and I know I'm definitely excited! However, let's take a quick trip back to 2009, when the original Just Dance was released. There are a lot of great songs, but I don't know who sung half of them!

The Challenge

Write a program that accepts a Just Dance song name from input and outputs the song's artist (as credited in-game.)

Here is the list of all songs and artists from Just Dance 1:
list pending

Rules and Assumptions

• You may assume that the song will always be valid.
• The song's title and artist must be properly capitalized.
• You may not read any external files - the song data must be hardcoded.
• If a song is covered (which several have been for various reasons), the program should return the cover artist (as they are credited in the game.)

Test Cases

Input: Eye of the Tiger
Output: Survivor

Input: Fame
Output: Irene Cara

Bonuses

• Each game has had one song everyone was really excited about. This year, it's Ievan Polkka by Hatsune Miku. You get a bonus of -50 points if you accept this song as valid input.

• Just Dance is fun, but why should we stop there? If you additionally accept songs fron the rest of the main series (Just Dance 2, 3, Greatest Hits/Best Of, 4, 2014, and 2015, not including DLC and skipping over any duplicates), you get a whopping -2009 points. Here is the full list for those games:
  list pending

  • Note that this doesn't include Just Dance 2016 songs.
  • This can be combined with the other bonus to get a total of -2059 bytes.

Meta Questions

• Are the bonuses too big? (I'm mainly talking about the -2009 point bonus for including every song.)
• Has anything been left out?
• Is this enough of a challenge?

Answer 25

Literally just printing the source code

code-golfquine

Wait a second. We already have a contest where you print the source code. Right? Wrong.

The challenge

Print out the source code. Not to STDOUT, but to a physical printer.

The rules:

• You must write a complete program that prints out its own source code with a printer connected to the computer.
• No STDIN (or input of any kind), STDOUT, or STDERR.
• No standard loopholes (includes no file input). No using lp(r/d) or similar commands.
• The printed code should be a reasonable size (between size 8 and 18) and a legible font (pretty much means no wingdings).
• You may assume that the user doesn't cancel the process and answers affirmatively to any system print dialogs.
• You can assume that the printer works, is ready, doesn't need new ink/paper, etc.
• If the language doesn't support printing, it is ineligible.
• This is code-golf so shortest code, in bytes, wins.

Answer 26

Print a sourcecode

code-golfquine

Given 2 inputs(First input is truthy/falsy, second input is program in same language as submission):

1. If the first input is truthy then transform the second input into same program but printing the source code(After modification) first.
2. If the first input is falsy then transform the second input into same program but after the program finished it prints the source code(After modification). If the program doesn't halt, you may or may not modify the program.

It's code-golf, so the shorter answer is the winner.

For example in CJam, I don't write the program to do this. (> means output)

0 q
>{"_~"q}_~
0 0 1{_@+}11*;
>{"_~"0 0 1{_@+}11*;}_~
1 q
> {q](\o"_~"}_~

Answer 27

Restricted "Hello, World!"

answer-chaininghello-worldrestricted-source

The task is very simple, output Hello, World! to STDOUT. The thing that makes this different are the rules:

• You need to provide a full functioning program, taking no input and outputting via STDOUT.
• The program must not write anything to STDERR
• The maximum amount of bytes you can use is 50
• The program may only contain printable ASCII characters. Programs using CP437 and other encoding systems are not allowed
• If a programming language is already used, you cannot use this same language again.
• You cannot use any character of the prohibited character list. This is the twist:

Prohibited character list (PCL):

The prohibited character list is a list full of characters, which cannot be used in the following programs. For example:

If the list was: He\., you need to create a program, without the characters H, e, \ and .. These are not case-sensitive.

If you succesfully manage to write a program that doesn't use any characters, you may add new one character to the prohibited character list.

e.g.

If the old PCL was He\., and you managed to write a program that doesn't use any of these characters, you may add a new character to this list. For example (whitespace). The new PCL will be He \. (notice that the whitespace character is added).

Posting Snippet:

This might help you wit posting your submission:

#[Language Name], N bytes

 [code]

 (explaination etc.)

 Added character: [char]

 New PCL: [list + new char]

In the beginning, the PCL is empty. The last person who managed to create a program without a new program made in 2 days, wins!

---

I'm not really sure if it is flawed or not. If you have any suggestions or comments, feel free to post them below in the comment section :)

Answer 28

What day of the week is Christmas?

Christmas is coming quickly, which leads to the question, what day of the week is Christmas this year? But what day of the week is Christmas for any year? Write a program that can do this. This is code golf, so the shortest code wins!

However, there is a major twist. No builtin functions to do this task is allowed!

Bonuses:

1. If the program can handle B.C. years as negative numbers, then -25%
2. If the program prints "The first Christmas!" for an input of -4 (4 B.C. is assumed to be when Jesus Christ was born), then -30 bytes
3. If, for some reason, you really like builtins, +90%! So try NOT to use it!

Answer 29

Broken FizzBuzz - Greg Is Confused underhanded code-golf popularity-contest

(FizzBuzz suggested by quartata in chat)

(Related: Deletion of a blank line in source code which causes unexpected functionality, What? No error?, and Write a line in program that looks useless)

Meet Greg. Greg is the new debugger at your company, and he deals with checking programs to see if they work. If they don't, he tries to find out why and fix them.

Greg is rather new to programming and understands the basics, but still gets tripped up by some advanced things. Sometimes, programs don't work and he doesn't know why.

You don't really like Greg, so you decide to play a game. You create two nearly-identical FizzBuzz-style programs - one which works, and one which doesn't.

For example:

n = input()
if (n % 3 == 0) {
 print "Fizz"
}
if (n % 5 == 0) {
 print "Buzz"
}

works, but

n = input()
if (n % 3 = 0) {
 print "Fizz"
}
if (n % 5 == 0) {
 print "Buzz"
}

doesn't. Greg is confused (but not by something as simple as this).

And because Greg has a desk only a few feet away from you, your code must be as small as possible, so he doesn't catch on.

Rules

• Your correct program must accept an integer as input and return output as specified below, and your incorrect program must do something else (such as throwing an error or giving invalid output).
  • The valid program's output must print "Fizz" if the number is divisible by 3, "Buzz" if it divisible by 5, "FizzBuzz" if it divisible by both 3 and 5, and nothing if it isn't divisible by 3 or 5.
  • The invalid program's output may do anything else.
• Greg knows all programming languages to date, including super-obscure ones. Therefore, your answer may be in any language you choose (providing it was created before this challenge was posted.)
• You MUST have the two programs be nearly identical, except for one small change. The more concealed or insignificant-looking, the better.
• Greg uses PPCG and has participated in underhanded challenges before, so he knows about the C trigraph (??/). You can't trick him with it.
• Greg has also seen replacing ASCII characters with nearly-identical Unicode or abusing fonts, meaning that won't work either. Therefore, your program's change must work with all fonts, any may not exploit visual similarity between characters with different code-points.
  • Changing an a to an A is allowed, as long as it's not obvious that that's what broke the program. However, changing a to <unicode character that looks exactly the same> is forbidden.
• Both programs must be written in the same language with the same version.
• Your answer must include:
  • The language both programs are written in
  • Two programs: one FizzBuzz program, and another that is broken
  • How to run both of them (the commands must be identical with identical arguments)
  • Why one doesn't work (in spoilertext)
  • The output of the broken one
• Your programs must have a Levenshtein distance of no more than 10 from one-another. (Meaning that you may add, delete, or change up to 10 characters in the broken code from the correct one.)
• Your score is the total bytecount of both of your programs.
• The winner is the post with the smallest score over 20 votes.

Meta Questions

• Is 10 too small a maximum Levenshtein distance? I was also considering 15.
• Are any of my rules already forbidden by the standard loopholes? I'd like to remove them if possible to make the post shorter.
• Similarly, should I remove or change any of my rules?
• This is a code-golf version of this previous edit. Should I keep it as code-golf or change it back?

Answer 30

Golf A Wiki

The Challenge

Golf a wiki. A wiki, for the purposes of this contest, is defined as a website with:

• Content editable by all
• Easy CamelCase (defined as a word with two capitals) linking
• Different pages or articles that are the targets of the links

Your wiki can be a self-contained HTML file (e.g. TiddlyWiki), or a cgi-bin script (e.g. SigWik).

Scoring

Your score is the size of your program in bytes, divided by the number of extra features implemented plus one.

The possible extra features are:

• Page history
• Syntax for "nowiki", that is, something like <\noscript> in HTML that makes the text inside it not be wiki syntax.
• A page list
• A find page facility
• Usernames and passwords (with registering)
• Security levels (requires usernames and passwords, or possibly IPs?)
• Delete pages
• Change page titles
• Redirects
• Random page
• Non-HTML formatting that is not just links [Should I remove this? I doubt it will be done.]

Lowest score wins, as this is code golf.

DISCLAIMER

ANSWERS WILL PROBABLY CONTAIN MAJOR SECURITY FLAWS. ONLY USE ON PRIVATE PORTS, UNLESS YOU WANT YOUR COMPUTER AND VERY POSSIBLY YOUR WHOLE NETWORK TO GET DESTROYED (FIGURATIVELY). [Is this too forceful?]

code-golf