Sandbox for Proposed Challenges

Question

This "sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to main. This is useful because writing a clear and fully specified challenge on your first try can be difficult, and there is a much better chance of your challenge being well received if you post it in the sandbox first.

Sandbox FAQ

Posting

To post to the sandbox, scroll to the bottom of this page and click "Answer This Question". Click "OK" when it asks if you really want to add another answer.

Write your challenge just as you would when actually posting it, though you can optionally add a title at the top. You may also add some notes about specific things you would like to clarify before posting it. Other users will help you improve your challenge by rating and discussing it.

When you think your challenge is ready for the public, go ahead and post it, and replace the post here with a link to the challenge and delete the sandbox post.

Discussion

The purpose of the sandbox is to give and receive feedback on posts. If you want to, feel free to give feedback to any posts you see here. Important things to comment about can include:

• Parts of the challenge you found unclear
• Comments addressing specific points mentioned in the proposal
• Problems that could make the challenge uninteresting or unfit for the site

You don't need any qualifications to review sandbox posts. The target audience of most of these challenges is code golfers like you, so anything you find unclear will probably be unclear to others.

If you think one of your posts requires more feedback, but it's been ignored, you can ask for feedback in The Nineteenth Byte. It's not only allowed, but highly recommended! Be patient and try not to nag people though, you might have to ask multiple times.

It is recommended to leave your posts in the sandbox for at least several days, and until it receives upvotes and any feedback has been addressed.

Other

Search the sandbox / Browse your pending proposals

The sandbox works best if you sort posts by active.

To add an inline tag to a proposal, use shortcut link syntax with a prefix: [tag:king-of-the-hill]. To search for posts with a certain tag, include the name in quotes: "king-of-the-hill".

Answer 1

Queuing queues

I recently found a great site, Dubtrack, for all my music needs. However, it features a very interesting method of ordering, which contains a queue of users, and each user has their own personal queue.

The user queue loops through each of the users that have songs, and plays the top song from their individual queue. This means that:

1. When there is a single user, it simply plays the songs in the order that user added them.
2. When there are multiple users, it interleaves the songs.

However, users' queues aren't always filled, and when a user adds his first song to the queue, the user is added to the end of the user queue.

For example, say there were 3 users each with the following queues (at time 0):

0 [1,10,100,1000]
0 [2,20]
0 [3,30,300]

then the resulting playlist would look like:

[1, 2, 3, 10, 20, 30, 100, 300, 1000]

However, if a user were to add his queue during the 4th song:

0 [1,10,100,1000]
0 [2,20]
0 [3,30,300]
3 [4,40,400,4000]

Then the playlist would look like

                      v New user's song finally plays
[1, 2, 3, 10, 20, 30, 4, 100, 300, 400, 1000, 400, 4000]
          ^ New user added here, but user 2 and 3 are still in front

Your challenge is to take a list of queues and join times, and return them in single playlist. You are guaranteed that there will be at least 1 queue at time 0, and that additional users won't be added after all the songs have played.

Test cases

Input
0 [1,5,3,7,2,6,3]
Output
[1,5,3,7,2,6,3]

Input
1 [3,6,9,12]
0 [4,10]
Output
[4,10,3,6,9,12]

Input    
0 [1,10,100,1000]
0 [2,20]
0 [3,30,300]
3 [4,40,400,4000]
Output
[1,2,3,10,20,30,4,100,300,400,1000,400,4000]

Input
11 [3000]
3 [6,8,10,11,0]
5 [4,100,14,12,0]
0 [0,1,2,3,4,5]
11 [2000]
Output
[0,1,2,3,6,4,8,4,5,10,100,11,14,3000,2000,0,12,0]

Answer 2

Natural Language Calculator

code-golf

Background

You are working at Wolfram Alpha, when a big fire occurs, wiping out much of the hardware infrastructure, losing much of the code. Now you are assigned to the natural language team working on writing new code for converting natural language to mathematical expressions to be evaluated. You must parse the following commands and even do mixed commands!

Challenge

The input will be a string, obviously. For multiple operations, there will be commands within input of commands.

Pi and e are simply inputted as "pi" and "e". Other special numbers are not needed to be handled.

Parse the following commands:

• Add x and y
• Subtract x and y
• Multiply x and y
• Divide x and y
• Factorial of x
• x factorial
• Exponent base n of x
• Log base n of x
• Natural log of x

You must deal with it case-insensitively. For example "5 Factorial" gives the same result ad "5 factorial" or "5 FAcTorial".

Testcases

> "Add 4 and 5"
9
> "Multiply 6 and 10"
60
> "Divide 144 and 12"
12
> Exponent base 10 of 3
1000
> 3 factorial
6
> 3
> Add 5 factorial and 2
122
> Exponent base e of natural log of e
e
> natural log of e
1

Answer 3

How many swaps do I need to sort a list?

code-golfarray-manipulationsorting

A swap is defined as an operation on a list that exchanges the position of exactly two elements:

[9, 1, 3, 4, 0, 0, 3, 7, 9, 1, 4, 4, 8, 7, 3, 9, 4, 7, 0, 1]
       | <----------------> |
[9, 1, 1, 4, 0, 0, 3, 7, 9, 3, 4, 4, 8, 7, 3, 9, 4, 7, 0, 1]

Of course, every list can be sorted via some sequence of swaps (e.g. that's how Shell sort works).

Given a list of single-digit integers, determine the minimum number of swaps you need to sort the list.

You may write a program or function, taking input via STDIN (or closest alternative), command-line argument or function argument and outputting the result via STDOUT (or closest alternative), function return value or function (out) parameter.

Input may be in any convenient, flat list format, as long as the data is not preprocessed.

Standard code-golf rules apply.

Test Cases

(will follow)

Sandbox Questions

• If the list elements are distinct, this is simply: a) determine ordering, b) treat ordering as permutation and decompose into cycles, c) subtract one from each cycle's length and sum the results. (Which would make this a duplicate.) Off the top of my head, I can't think of a similarly simple algorithm when duplicates are allowed. Can anyone else?

Answer 4

Employee Scheduler

This challenge is simple: make a schedule for the student workers in my department!

Student workers have to regularly update their availability to accommodate class changes every semester, and the number of student workers we have employed constantly varies. Also, student workers are not allowed to work more than 20 hours a week. Meanwhile, there are several stations that need to be manned throughout the work day.

Required Minimums:

Your program should at least be able to do the following:

1. Input a list of first names and times of availability
2. Output a one month schedule that covers 4 stations 5 days a week from 800 to 1700

If there is a gap of time that cannot be filled based on the availability given, you should fill that gap with an obvious name like "NEEDED" or something like that. Note that the times of availability will depend on the day of the week.

Your program does need to able to at least run in Windows. Also, your program absolutely may not schedule workers more than 20 hours in a week.

You may assume that all student workers have been trained in all stations, so anybody can work anywhere. You also may assume that the month for which you should generate a schedule is following month (so if it is January, make a schedule for February).

Other Notes:

You'll notice I'm not specifying an IO method you must use. I trust you as a coder to pick a method that suits your program, just keep in mind this is a popularity contest and ease of use is an inevitable factor. Also, you may use 12 or 24 hour time at your discretion. Please list both the method of IO and 12 or 24 hour time in your description.

Some things that I'm not requiring, but would definitely earn some kudos from me:

• Use a station priority system when creating the schedule (some stations should be covered before others)
• Try to maximize the hours given to each student (while not going over 20 hours per week, of course)
• Minimize overlap
• Make your output pretty (currently we use an excel spreadsheet that looks pretty nice)
• Input the number of stations
• Input the month for which to generate
• Generate multiple months (using the same availability)
• Input holidays and days the department is closed
• Make your program run on both Windows and OS X
• Golf your program

Examples

INPUT:

Jack    m:0900-1530 t:0800-1530 w:0900-1200 th:0800-1530 f:0900-1700
John    m:0000-0000 t:1300-1700 w:0900-1200 th:1300-1700 f:1000-1200
Joseph  m:0800-1000 t:1300-1700 w:0000-0000 th:1300-1700 f:0800-1000
Jannett m:1430-1700 t:0000-0000 w:1200-1700 th:1100-1400 f:1200-1700
Brianna m:0900-1430 t:0800-1300 w:0900-1430 th:0000-0000 f:1200-1700
Dianne  m:0800-0900 t:1300-1700 w:0000-0000 th:1300-1700 f:0800-1000
Megan   m:1400-1545 t:1100-1700 w:1400-1545 th:1100-1700 f:0000-0000
Sierra  m:1600-1700 t:0800-1100 w:0900-1300 th:0000-0000 f:0800-1300
Sandy   m:1345-1700 t:0800-1045 w:1345-1700 th:0800-1045 f:1200-1700
Holly   m:0800-1200 t:0800-1200 w:0000-0000 th:0800-1200 f:0800-1200

OUTPUT:

Monday              Tuesday          Wednesday        Thursday        Friday

STA 1               STA 1            STA 1            STA 1           STA 1
Joseph 8-10         Holly 8-1130     Brianna 9-1430   Jack 8-11       Joseph 8-10
Jack 10-1430        Brianna 1130-13  Jannett 1430-17  Megan 11-17     Holly 10-12
Jannett 1430-1700   Joseph 13-17                                      Desiree 12-17

STA 2               STA 2            STA 2            STA 2           STA 2
Riane 8-9           Sierra 8-11      John 9-12        Holly 8-11      Sierra 8-1
Brianna 9-1430      Megan 11-17      NEEDED 12-1430   Jannett 11-2    Brianna 13-17
Megan 1430-1545                      Megan 1430-1545  Joseph 14-17    
NEEDED 1545-16                       NEEDED 1545-17
Sierra 16-17

STA 3               STA 3            STA 3            STA 3           STA 3
Holly 8-12          Sierra 8-1045    Holly 8-12       Sierra 8-1045   Riane 8-10
NEEDED 12-1345      NEEDED 11-13     Sierra 12-1      Jack 11-1       Tyler 10-12
Sandy 1345-17       Riane 13-17      NEEDED 13-1345   Riane 13-17     Sandy 12-17
                                     Sandy 1345-17

STA 4               STA 4            STA 4            STA 4           STA 4
NEEDED 8-9          NEEDED 8-13      NEEDED 8-9       NEEDED 8-13     NEEDED 8-9
Jack 9-10           John 13-17       Jack 9-12        John 13-17      Jack 9-14
NEEDED 10-1430                       NEEDED 12-17                     NEEDED 14-17
Jack 1430-1530
NEEDED 1530-17

As you can see, in this case the input 0000-0000 means that person is not available on that day of the week.

Answer 5

There's an App SE Site for that

code-golfkolmogorov-complexityinternetstack-exchange-apifile-system

Oftentimes, when searching through StackExchange, I find myself seeking to post a question about something or another, but not knowing where to post it. That's where you come in.

The Challenge

Write a full-functioning program that does the following:

1. Takes an input string
2. Attempts to find suitable SE sites relevant to the input string (this is very flexible, but should not be returning English.SE for questions about Coffee, for example)
3. Attempts to find 3 questions on each suitable site that may relate to the input string (should match the list of questions if I searched in the search bar of each site, sorted by number of votes)
4. "Output" is a folder tree written to disk with the following qualities:
   • The highest folder of the tree should be named the input string.
   • The second-highest layer should consist of folders named the same as the sites on which the input string was found suitable.
   • The third layer should be <=3 .md files that are named the same as the questions found when searching through the suitable sites, the contents of which are the question's markup content.

Rules

• You MUST query for this information. I don't want 50EB solutions.
• "Suitable sites" are defined as the keyword appearing in the site description.
• Run time should be <5 minutes for >3 MB internet speed.

Bonuses

There are no bonuses.

Remember - SE is a big place now, and, as of such, we must compensate with short code. This is code-golf, everybody, so the shortest solution wins!

Answer 6

Monophonic Pitch Detection

Tags: code-challenge test-battery

Sandbox Notes

• Still in progress. I haven't made any of the test cases or snippets yet.
• This is intended to be an easier and more accessible alternative to Polyphonic Pitch Detection.
• Would this still be a duplicate of the polyphonic version? Solutions could "work" in both challenges, but algorithms that work for this one would perform extremely poorly (typically monophonic algorithms fail outright with multiple waveforms and produce a completely incorrect frequency) for the other.

---

Take an array of samples, and output the frequency of the waveform found in the samples.

---

You will receive a list of samples as signed 16-bit integers at a fixed sample-rate of 44100 samples-per-second. Each input will only contain one waveform in the range of 100hz to 2000hz.

You must output the frequency detected (in hertz) with up to 2 decimal places of precision.

Test Cases

Each test case is on it's own line. Each line begins with the name of the test case, followed by a semi-colon (;), then the frequency present in the test case (with 2 decimal places of precision), followed by another semi-colon, then the samples separated by commas:

Test Case Name;123.45;3,75,1234,56789,4321,-23,-408,-9266,41,0,etc...

(link to test case file, will include synthesized waveforms, real instrument sounds, added noise, different pitches)

Scoring

The score of a submission is a percentage based on how close the submission's results are to the actual frequency of each test case. Specifically it will calculated using the formula in the snippet below (use this to calculate your score):

(snippet for calculating score)

Rules

• No built-ins that detect pitch or extract waveform frequencies are allowed.
• Helper functions that are designed to aid frequency analysis like FFT are permitted.
• You may optimise your solution for the test cases, but you cannot hard-code the results for these specific test cases.

Play Samples

You can hear what a list of samples sounds like by pasting it into this snippet:

(snippet for playing sample strings or sine waves using web audio)

Links

• Overview of Pitch Detection Techniques
• Autocorrelation
• YIN Algorithm

Answer 7

Letter subsets

code-golf kolmogorov-complexity

Consider two letters, L1 and L2. L1 is a solid subset of L2 if and only if all of the lines can be placed on L2 without rotating or breaking L1 or marring the image of L2; this is L1 s.s. L2, symbolically. For example, I s.s. T because you can place the line of I on T without a difference, and C s.s. O for the same reason. Here are all the letters (L1, L2) for which L1 s.s. L2 and L1 ≠ L2:

L1  L2
F   E
C   O
I   T
I   L
O   Q

Two letters L3 and L4 share the relation of variant subset (i.e. L3 is a variant subset of L4, or L3 v.s. L4) if and only if some rotation of L3 exists where L3 s.s. L4. Here are all the letters (L3, L4) for which L3 v.s. L4 and L3 ≠ L4:

L3  L4
F   E
C   O
I   T
I   L
O   Q
V   A
I   H
H   I
I   N
I   M
I   B
I   V
I   X
I   Z
I   P
I   E
I   W
I   R
I   K
I   F
I   D
N   Z
Z   N
T   H
G   Q

Specs

Your input will be two letters. You may take them as a string, two characters, or two numbers representing those characters, as arguments, read from STDIN, or from a file. With these two letters, you are to output their relation. You should favor s.s. over v.s. over nothing. Your output will be ss, vs, or nothing. Your program may do anything if the input is not a pair of uppercase letters. Your program should pass all of the above relations when given those letters as input.

---

~META~

Suggestions? Any letters in v.s. or s.s. I missed? Any you don't understand?

Answer 8

Reasoning

code-golf

Introduction

Reasoning is one of the most important human capabilities, often counted as what separates us from other species. This capacity, however, takes up a substantial portion of our meaty brain. Your challenge is to recreate a reasoning system in a much abbreviated form.

Definitions

The challenge, is, given a universe of objects and n-ary relations and a set of facts and laws on the relations, to determine whether a hypothesis is a fact or not. The language in which these are expressed are drawn from the alphabet "012345789RC@ " under the following rules (in EBNF with an ad-hoc expansion).

1. An unbound-variable is denoted by a sequence of digits denoting a non-negative integer. For example, 3 is a variable which we may read as "object 3".

   natural = non-zero-digit , { digit } ;

   unbound-variable = natural ;

2. A bound-variable is denoted by a "@" followed by an unbound variable.

   bound-variable = "@" , unbound-variable ;

3. A variable is either a bound-variable or an unbound-variable

   variable = bound-variable | unbound-variable ;

4. A relation-identifier is denoted by a capital "R" followed by a single digit denoting its arity and then a natural number identifying it.

   relation-identifier(n : digit) = "R" , n , natural ;

5. A relation is denoted by a relation identifier followed by a sequence of variables whose length matches its arity.

   relation = relation-identifier(a) , a * { " " , variable } ;

6. A consequence is denoted by a capital "C" followed by two relations.

   consequence = "C" , relation , relation ;

7. An expression is either a consequence or relation of that magnitude.

   expression = consequence | relation ;

The inference rules are the following:

1. From C R R' and R (where R and R' are relations) to infer R'.

2. From E to infer E{@m=p} where E{@m=p} is the expression E with all instances of bound-variable @m replaced by variable p.

The Challenge

You will be given a sequence of at least one expression, that will be provided as a newline separated strings on the stdin. The first of these will be a relation with no bound variables -- the hypothesis. The remaining expressions are the facts. Your program must indicate whether the hypothesis can be infered from the facts or not. It does this by printing any of the following strings to the stdout: "true" (case-insensitive), "+", "1", "yes". Any other input will be interpreted as claiming the hypothesis cannot be infered from the facts.

Test cases

>input:
R00
>expected output:
false|no|whatever

>input:
R00
R00
>expected output:
true

>input:
R10 0
R10 @1
>expected output:
true

>input:
R20 4 9
R20 9 4
CR20 9 4R20 4 9
>expected output:
true

>input: 
R2859 7 163
R2859 @0 163
>expected output:
true

>input:
R10 5
R10 1
CR10 1R10 2
CR10 2R10 3
CR10 3R10 4
CR10 4R10 5
>expected output:
true

>input:
R10 6
R10 1
CR10 1R10 2
CR10 2R10 3
CR10 3R10 4
CR10 4R10 5
>expected output:
false   

>input
R20 4 5
R20 9 6
CR20 6 @0R20 7 @0
CR20 @0 7R20 @0 4
CR20 @0 9R20 5 @0
CR20 @0 @1CR20 @1 @0
>expected output: 
true

>input
R20 4 5
R20 9 6
CR20 6 @0R20 7 @0
CR20 @0 7R20 @0 5
CR20 @0 9R20 5 @0
CR20 @0 @1CR20 @1 @0
>expected output: 
false

Grading

This is a golf competition, the fewest number of bytes wins. Other restrictions are TBD.

Answer 9

Determine if a given loan repayment schedule is a weekly or a daily schedule?

Problem scope

Its a real life problem which I recently fixed with >90% accuracy but wants to know if there can be near to 100% accurate result. Winner will be the one that can show using datasets that his solution will give minimal failures.

Problem Description

You are given a set of repayment schedules, some of which represents a daily repayment schedule and some represents a weekly repayment schedule. Each repayment schedule is in its own file and you need to segregate the repayment schedule files in 2 buckets, daily and weekly.

No repayment would be received on bank holidays which include weekends.

A weekly repayment schedule means that borrowers have agreed to make regular fixed repayments on a particular weekday every week. A Daily repayment schedule means that borrowers have agreed to make a fixed repayment on all working days till loan gets repaid fully.

Few Borrowers may do one of these besides doing regular repayments.

1. Choose not to return on some scheduled repayment days.
2. Choose to make only partial repayment on some scheduled/unscheduled repayment days.
3. Choose to make extra repayment to catch up on previous payment or just doing prepayment.
4. May skip making any payment for extended duration.

Off course, not everyone will do all, but in real life people sometimes are not able to make payments or sometimes do catch up or part payments. At the same time, most borrowers would stick to payment schedules for most of the time of the return duration.

A sample demonstrating above conditions from a daily repayment schedule could be as follows for a person not completely regular

Date Repayment amount

1-Feb-2016 500

2-Feb-2016 500

4-feb-2016 500

8-Feb-2016 400

10-Feb-2016 1000

10-Mar-2016 500

11-Mar-2016 500

A sample demonstrating above conditions from a weekly repayment schedule could be as follows for a borrower not completely regular

Date Repayment amount

1-Feb-2016 500

8-Feb-2016 500

17-feb-2016 500

22-Feb-2016 400

07-Mar-2016 1000

14-Mar-2016 500

11-Mar-2016 500

This real life problem is related to repayment schedule of low income borrowers where anomalies like above can be considered fair owing to their meager means. The sample above are only small part of the file, not the whole file.

I have clarified some doubts at https://codegolf.stackexchange.com/questions/71334/determine-if-a-given-loan-repayment-schedule-is-a-weekly-or-a-daily-schedule . Check those if possible.

Answer 10

Is the plate balanced? code-golf

Task

Given a grid of 1 digit numbers and a coordinate, tell me if it is balanced.

How to balance check

Explanation coming. I know how it works for 1d (Balance a set of weights on a seesaw), but don't know how it would work for 2d.

Input

Input will be a grid of 1 digit numbers. Each number corresponds to the amount of weight at that location.

Examples

Input:
111
111
111
1,1

Output:
truthy

Answer 11

Sloppy Shuffle

Write a program that will shuffle the numbers from 1 to 52. Rather than from your language's random facility, the result will be determined by the input. But not in any particular way -- however you choose!

The Rules

• The program must accept all possible (finite) inputs. It doesn't matter if it is empty, or the result of monkeys with typewriters, or anything in between. Literally any input must be accepted without (unhandled) errors.
• For each of the 52-factorial possible ways of shuffling the numbers, there must be at least one finite input that will make your program produce this permutation.
• No matter what (finite) input is given to the program, it must produce some permutation of the numbers.
• If given the same input, the program must always produce the same permutation.
• Nothing should be produced on stderr.
• Standard restrictions apply.

Input/Output

Default input methods (such as stdin or command line args) are acceptable. If using stdin, any finite input from stdin must be accepted (although it doesn't all have to be read). For other input methods, use your best judgement in accepting arbitrary binary or string data as appropriate.

Default output methods (such as stdout) are acceptable. The form of the output should be the number from 1 to 52 in some order corresponding to the permutation as appropriate for your output method.

Scoring

This is code golf. The shortest answer in bytes wins!

However, in case of a tie in code length, the first tiebreaker is the maximum over all permutations of the minimum input length needed to generate that permutation. The program that has a larger minimum input wins.

(That may have been confusing, so an example: if program A can generate any permutation with no fewer than 100 bytes of input, but program B needs at least 1000 bytes to generate the identity permutation, program B wins the tie.)

Example

This is an example of a program which fulfills the requirements in Lua:

-- return a number from (1,n) depending on input
local function pick_from(n)
  local str = io.read() or ""

  -- always proceed even if input is not a number
  local num = math.floor(tonumber(str) or 0)

  -- guard in case of parsing overflow (e.g. input of 1e99999999999)
  if num ~= num or num > 1000 or num < -1000 then
    num = 0
  end

  return 1 + (num % n)
end

-- create a list of 52 numbers
local deck = {}
for i = 1, 52 do
  deck[i] = i
end

-- Fisher-Yates shuffle algorithm
for i = 52, 1, -1 do
  local j = pick_from(52)
  if i ~= j then
    deck[i], deck[j] = deck[j], deck[i]
  end
end

for i = 1, 52 do
  print(deck[i])
end

Notice that although I used the Fisher-Yates algorithm, the property that Fisher-Yates generates a permutation uniformly is irrelevant to the correctness of the program.

Another note -- if you never read at least log2(52!) bytes from the input, it is probably impossible for your program to generate all permutations.

Answer 12

How clean is my snow? code-golf

_{Idea shamelessly take from https://codereview.stackexchange.com/questions/118538/how-clean-is-my-snow#comment221029_118538}

---

The challenge

Your challenge is to tell how clean my snow is. Unclean snow is any snow that is not pure white. This would be super easy except for one hiccup, not all of the image is a picture of the snow, in the case of the image above some of the image is the sky (can't you tell? I'm such a good artist!).

Determining where the background is

[Write-up coming, it has to do with how large the splotch is and finding the biggest white spot, so the clouds don't count]

Answer 13

ToUpperCase... Mathematica style

For this challenge, you must write a program or function that converts every character in a string to upper case. "Wouldn't this be too broad/a duplicate/etc.?" you ask. Nope; you have to exactly implement Mathematica 10.1's ToUpperCase function!

Note

ToUpperCase works quite peculiarly on Unicode. For example, ß converts to SS! The full replacement list (from:to(,to);):

97:65;98:66;99:67;100:68;101:69;102:70;103:71;104:72;105:73;106:74;107:75;108:76;109:77;110:78;111:79;112:80;113:81;114:82;115:83;116:84;117:85;118:86;119:87;120:88;121:89;122:90;223:83,83;224:192;225:193;226:194;227:195;228:196;229:197;230:198;231:199;232:200;233:201;234:202;235:203;236:204;237:205;238:206;239:207;240:208;241:209;242:210;243:211;244:212;245:213;246:214;248:216;249:217;250:218;251:219;252:220;253:221;254:222;255:89;257:256;259:258;263:262;269:268;271:270;275:274;277:276;283:282;301:300;305:73;322:321;328:327;337:336;339:338;345:344;353:352;357:356;367:366;369:368;382:381;945:913;946:914;947:915;948:916;949:917;950:918;951:919;952:920;953:921;954:922;955:923;956:924;957:925;958:926;959:927;960:928;961:929;962:931;963:931;964:932;965:933;966:934;967:935;968:936;969:937;977:920;981:934;982:928;987:986;989:988;991:990;993:992;1008:922;1009:929;1013:917;8458:63350;8467:8466;8495:8496;8500:63358;63154:63344;63155:8492;63156:63346;63157:63347;63159:8497;63161:8459;63162:8464;63163:63353;63164:63354;63166:8499;63167:63357;63169:63359;63170:63360;63171:8475;63172:63362;63173:63363;63174:63364;63175:63365;63176:63366;63177:63367;63178:63368;63179:63369;63180:63370;63181:63371;63182:8493;63183:63373;63184:63374;63185:63375;63186:63376;63187:8460;63188:8465;63189:63379;63190:63380;63191:63381;63192:63382;63193:63383;63194:63384;63195:63385;63196:63386;63197:8476;63198:63388;63199:63389;63200:63390;63201:63391;63202:63392;63203:63393;63204:63394;63205:8488;63206:63396;63207:63397;63208:63398;63209:63399;63210:63400;63211:63401;63212:63402;63213:63403;63214:63404;63215:63405;63216:63406;63217:63407;63218:63408;63219:63409;63220:63410;63221:63411;63222:63412;63223:63413;63224:63414;63225:63415;63226:63416;63227:63417;63228:63418;63229:63419;63230:63420;63231:63421;63232:74;63488:63514;63489:63515;63490:63516;63491:63517;63492:63518;63493:63519;63494:63520;63495:63521;63496:63522;63497:63523;63498:63524;63499:63525;63500:63526;63501:63527;63502:63528;63503:63529;63504:63530;63505:63531;63506:63532;63507:63533;63508:63534;63509:63535;63510:63536;63511:63537;63512:63538;63513:63539;63572:63540;63573:63541;63574:63542;63575:63543;63576:63544;63577:63545;63578:63546;63579:63547;63580:63548;63581:63549;63582:63550;63583:63551;63584:63552;63585:63553;63586:63554;63587:63555;63588:63556;63589:63558;63590:63558;63591:63559;63592:63560;63593:63561;63594:63562;63595:63563;63596:63564;63604:63547;63608:63561;63609:63555;63614:63613;63616:63615;63618:63617;63620:63619;63621:63549;63622:63556;63626:63544;

Rules

• You cannot use a built-in that completely solves this challenge.
• If a function is written, the input is guaranteed to be a single string or equivalent.
• All characters not specified in the replacement list are to remain unchanged.
• All codepoints will be less than U+10000.
• If and only if your language can only take bytes as input, the string will be encoded in UTF-8.
• Standard loopholes are disallowed.
• Have fun!

Test cases TBD

Meta Questions

• What are some good test cases for this challenge?
• Is there something that I possibly missed while writing this challenge?

Answer 14

Use Simpson's Rule

Simpson's rule is a fairly simple method for approximating a definite integral of one variable. The idea is to approximate the function to be integrated by a series of interpolated parabolas, and then find the area under those.

As I learned in first-year calculus, the form of Simpson's Rule we'll be using is:

where the width of each interval is h.

Equivalently, this is the dot product with the vector h/3([1,4,2,4,...,1]) the same length as the input.

Input

• An array of n>1 real numbers representing the values of f at x-values equally spaced by h. n will be odd.

• h, a positive real number.

Output

The area approximation that Simpson's Rule gives.

Test cases

[0,0,0], 1 -> 0
[3,1,4,1,5], 1 -> 8

[add more]

Answer 15

Implement the Block Sort sorting algorithm

code-golf

Block sort is an interesting sorting algorithm (comparatively speaking). Here are some of its important properties:

• O(n log n) time complexity in worst and average case
• O(n) time complexity in best case
• O(1) space complexity (not including the space that holds the list itself)
• Stable

If you check out this table comparing sorting algorithms, you'll see that it's the only one that has the whole row highlighted in green.

Your challenge is to write an implementation of the block sort algorithm in the fewest bytes.

Answer 16

Advent of Code, puzzle 1

I don't know if anyone here spent their December working on the problems found on Advent of Code, but I thought some of the simpler problems might make good code golf puzzles.

So, here's the first one. There will be two challenges, and the solution should be a pair of programs, each of which solves one challenge.

Score is based on the combined byte count of the two programs.

(An alternative would be to also allow a single program that produces a tuple of the two solitions- what do you think?)

Input: An unbalanced string of open and close brackets.

Output 1: The count of the number of open brackets take away the number of close brackets.

Output 2: The index of the first close bracket that causes the running sum to reach -1.

Answer 17

Knights and Knaves posted

Undeleted so that comments are visible

Answer 18

Diopter lenses

In photography, there are thin lenses that you put in front of a photographic lens to make it behave like a close-up lens. Each of these lenses has an associated diopter value which is a positive integer. If you stack two (or more) of these lenses you get an equivalent of a lens with the diopter value that is the sum of the values of those lenses.

The problem

Your program should take one diopter value n as an input. The input need not be validated.

You should output in any human readable form a list of diopter lenses such that:

• the maximum diopter value you can form by stacking the lenses is n,
• every diopter from 1 to n can be formed by stacking a combination of those lenses,
• there exists no set of fewer lenses that complies to the above rules.

An example

Given the input of:

6

Print the output of

1
2
3

Because:

1=1
2=2
3=3
1+3=4
2+3=5
1+2+3=6

The rules

This is code golf, so the objective is to write the shortest possible code, but, since there is a trivial solution that might not be obvious to some, I suggest that the answer be encoded by some means so one wouldn't see the solution before attempting to solve the problem.

Any type of output is accepted, as long as the program outputs correct clearly separated positive integers and no other alphanumeric character.

My solution

python 2, 52 bytes, base64 encoded

bj1pbnB1dCgpCno9MQp3aGlsZSAyKnotMTxuOnByaW50IHo7eio9MgpwcmludCBuLXorMQ==

code-golf, optimization, combinatorics

Answer 19

Plotting Dynamical Systems in ASCII

code-golf

Input:

• A Function to and from the real plane (henceforth R2) , call it F

• A point in R2 that is to be the center of a disk, call it c

• A radius, call it r

• An integer representing the number of iterations to be performed, call it n.

Output:

You are to output n+1 ascii "images". The first depicts the disk D (with center c and radius r) and the ith image depicts F^i(D), aka F(...F( F(D) )...) where we have applied F to D, and then applied F to F(D) and so on until we have applied F i times.

Input Details:

• F will always be polynomial. See below for acceptable examples.

• Any c = (c1,c2) given will satisfy |c1|<50 and |c2|<25.

• Also, r will always be small enough that D the disk around c with radius r will contain no points with an x coordinate greater than 55 or less than -55 and no y coordinate greater than 32 or less than -32.

• n will be positive and less than 5.

Output Details

• We will be looking at a rectangular subset of R2 given by { (x,y) : -60 <= x <= -60 and -33 <= y <= 33}. i.e. a rectangle with side lengths 120 and 66 centered at the origin.

• Each output image will contain 320*320 characters. This represents the above region in R2 with gradations of 0.5 along each axis.

• Each character will represent a single point in R2. For example if we just look at part of the first quadrant (with the axes labeled which you need not do)

      y
      ^
      |
      .............................
    7 .............................
      .............................
    6 .............................
      .............................
    5 .............................
      .............................
    4 ............................
      .............................
    3 .............................
      .............................
    2 .....................b.......     b =(10.5,2)
      .............................
    1 ..a..........................     a = (1,1)
      .............................     z = (0,0)
    0 z............................  --------> x 
      0 1 2 3 4 5 6 7 8 9 | | | | |  
                        10| 12| 14
                          11  13

• Points that are empty (i.e. not in F^n(D)) will be represented by the . character, whereas filled spaces will be represented by #.

• Each image will have the same or fewer # represented points in it because we will not be displaying points that are outside the region.

  How do these maps work?

These are iterative maps we will be dealing with. For each point # in a given image, to get the next image, you will apply the given map F to it. If the point leaves the viewing area, you need not render it. However if in a later iteration it should reenter the viewing area, it should reappear.

For the purposes of this challenge, the image of a point should be rounded to the nearest 0.5.

A map might be F(x,y) = (4x(1-x), x+y)

Answer 20

Hourglass simulator

code-golf

Write a full program or function to simulate an hourglass.

Input

n, the number of seconds on the hourglass.

Behavior

At the start, there are n seconds on a timer, and the timer is counting down. When the user presses the spacebar with t seconds left, set the time left to n-t. Terminate the program when time runs out.

This models an hourglass where the top of the hourglass is initially filled with n seconds of sand. When the spacebar is pressed, the hourglass flips by 180°. When either side of the hourglass runs out of sand, the program terminates.

[Is there anything I'm missing? This spec seems really short.]

Answer 21

Implement an SR NOR latch with Life-like rules

code-challenge

In Conway's Game of Life, there exist meta-pixels that can have any Life-like rule. Consequently, it is possible to simulate Conway's Game of Life with itself. It is also possible to build circuit-like structures, such as wires and logic gates by mixing together different Life-like rules in the right ways.

For example, one can simulate wires with three Life-like rules: B/S, B1/S, and B2/S (where the original Game of Life has the rule B3/S23). In the gif below, which shows one way to cross parallel wires, these rules are black, blue/cyan, and green/yellow, respectively.

Building such circuit components is a fun challenge, and I encourage you to try a couple logic gates, like AND or OR.

The Task

Your task is to construct an SR NOR latch, the most fundamental latch in circuitry. From Wikipedia:

• If there is no signal on either R or S, leave the outputs unchanged.
• If there is a signal on R (reset), the Q output turns off and the Qbar output turns on.
• If there is a signal on S (set), the Qbar output turns off and the Q output turns on.
• You may safely assume you will never get a signal on both R and S at the same time.

Now, I used the word signal repeatedly because there are different ways to do wires. You can use the B1/S + B2/S combination shown above (blue and green, respectively), or you can use a B1/S12 rule like this:

These methods and others have their advantages and disadvantages. This is part of the challenge.

The Rules

• If periodic input/output is chosen, then the output should have the same period as the input. As one of the output wires will always be "on", the output from this should be periodic and infinite (like a glider gun, say).
• You may assume that periodic signals are given with a period greater than the time it takes for the latch to flip.
• Steady input must be succeeded by steady output.
• You may not make the field toroidal in any way, except for demonstration, like the wire crossing example above. This is intended to disallow cheating by wrapping vertically so no wire crossing is needed.
• If the circuitry is periodic, you may assume the input signal arrives at the most convenient time.
• Initially, the Q output should be off and the Qbar output should be on.

Scoring

Precise details on how to weight these is to be determined.

• Fewer rules is better. The wire crossing example above has three rules: B/S for black, B1/S for blue, and B2/S for green.
• Smaller is better. Area will be considered, as in the minimum bounding box needed to contain all necessary pixels that are not part of a wire. For instance, the wire crossing example above has a bounding box that is 4 pixels wide (the tips of the wires - where there is a blue cell without a green sheath - are not included) and 9 pixels high, for a total area of 36 pixels.
• Faster is better. For this, count the number of generations from when the input arrives to when a fully formed output leaves. For the example above, this would be 9 units of time. Here is a gif of those 9 generations, including the one before.
  
• Lower latency is better. I define this to be the number of generations after a fully formed output leaves until the system has either stopped evolving or settled into a periodic pattern. The example above would have a latency of 2 generations. For periodic patterns, "settled" is defined to be when the system reaches the first pattern that will be repeated (the start of the cycle).

Note: I strongly recommend using Variations of Life for this.

Meta

• Additional clarifications needed?

Answer 22

Dice sums from side values

I rolled some dice and put them on the table with their sides touching and forming one object with 8 horizontal sides. This means I put the dice in one of these formations (up to rotations):

xx   x
xx   xx  xxx

I read the number pips on the 8 horizontal sides in counter clockwise direction. You should write a program or function that given the list of the 8 horizontal sides in counter clockwise order returns a list of possible sums of the top pips from the dice rolling.

The layout of a die is always the following:

    +---+
    | 1 |
+---+---+---+---+
| 2 | 3 | 5 | 4 |
+---+---+---+---+
    | 6 |
    +---+

For example if the input is 3 2 1 1 2 6 6 5 there are four possible configurations with top views:

623, 633, 643, 653 giving the output list 11, 12, 13, 14

with the sides always being

 566
3XXX2
 211

For the input 1 1 2 2 3 3 2 2 there is only one configuration with the top view:

46
31 giving the one element output list 14

Input

Output

Examples

This is code golf so the shortest entry wins.

Related code golf with a single die: Determine dice value from side view

Answer 23

Length of a month starting from a specific day

Given a date, you are to output the number of days from today, to the last date that has a number less than today next month.

It can be calculated this way:

• If the current date in the month is not more than the number of days next month, output the number of days in the current month.
• Otherwise, output the number of days in the next month + number of days starting from the current day in the current month.

This is code-golf. Shortest code wins.

Examples

2016-01-21  ->  31
2016-01-30  ->  31
2016-01-31  ->  30
2016-02-29  ->  29

---

Should leap years be supported?

Answer 24

Repeatedly convert from minimal base to base 36

fastest-codebase-conversionrepeated-transformation

Your task is to convert an input of a list of strings which represent arbitrarily large numbers from the lowest possible base to base 36, repeatedly, until there is no further change to be made.

Rules:

• You may not use base conversion builtins.
• From 0 to 35 in base 36 is defined as:

  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z

• All submissions will be tested on this cloud 9 workspace and should be uploaded for testing (along with any updates) on this GitHub repository.
• All submissions must be written for compilers/interpreters that:
  • Are free to use.
  • Do not take up excessive space.
  • Can run with simple installations on Ubuntu 14.04.

Test Cases:

Coming soon

Answer 25

Elementary Cellular Automata, My Dear Watson code-golf

A seemingly innocent dinner party composed of elementary cellular automata has just been turned into a murder mystery. One of the cellular automaton guests has killed the host! All that remains as evidence for who committed the crime is the nth generation of the perpetrator. Luckily for them, Sherlock Holmes is on the case.

Show Watson how it's done by taking an integer n, and a string representation of the nth generation of the murderous automaton and printing or returning a list of the possible suspects (the numbers representing the rule of each amphichiral elementary cellular automata, see the bottom of the linked page.)

Rules:

• The input string will have length 2n+3 for the nth generation.
• The first character of the string represents the values on the infinite tape to the left, and the last character of the string represents the same for the right.
• Assume that the automata start with a single 1 in the center of a string of all 0s.

Example

Generation 0 of every automaton:

010

Notes:

• I don't have a reference implementation yet, nor have I created any examples.

Answer 26

Binary Arithmetic Using Unary Operators code-golf restricted-source

This is based off a game I was playing with a friend a few years back. How many different mathematical operators can you implement using only unary operators in your source*. We were able to implement most basic arithmetic in C, but for this challenge you can use any language.

* Except under certain conditions, see below.

Specifics:

All binary operators are disallowed, except under the following conditions:

• Binary comparison operators are allowed as long as one operand is a constant (e.g. you can do if (x == 0) or if (x) but not if (x == y))
• You may use binary assignment to load user input, only at the start of your code, or if you create a binary = method using these rules.
• You may assume that all variables are default-initialized to 0; if your language does not default-initialize variables, you are allowed to set them to zero only at the start of your code.

Additionally, please note the following:

• You do not have to write a complete program if your language supports functions/methods.
• You can use other operators from your source (e.g. your implementation of * could use your implementation of +)
• Standard library functions follow these rules too (e.g. you can use sqrt(x) but not mod(x, y))

Scoring:

Your score is determined by the formula [code size in bytes] / [number of operators implemented]. So for example, a 300-byte program that includes the functions +, -, and * would count as 300/3 = 100. Lowest score wins.

Answer 27

[title TBD]

code-golf

Input

An integer n between 1 and [currently 1652; TBD at the time of posting the comic], inclusive.

Output

The XKCD title for comic number n. (This is the text written above the comic panel, i.e. the text content of the <div id="ctitle"> element, not the title-attribute value of the img element. Here's a handy list, though the actual comic on xkcd.com will govern if it differs from what's on that list. However, the title is displayed in caps and smallcaps due to CSS, and you must output it in caps and lowercase (respectively).)

(If by the time the question is posted there's a comics with an ampersand-escaped character reference — I don't think there are any now — then I'll also add a caveat about how the output of your program should include the actual character, not the ampersand-escaped reference.)

Obviously…

I/O can be by any standard means and in any standard format. And no using the Internet to look up the title.

Answer 28

The overall task will involve extracting market data for various trading instruments (represented by unique symbols), applying some transformations and statistical functions, and displaying the results in a report.

Obtain the following QUOTES series from Bashoop: TYQUOTES, FVQUOTES

The quotes data is stored as a BBO. BBO stands for best bid/offer, which represents the best bid and ask (ask and offer are interchangable terms) in the market for a given instrument at any given time. At each timestamp it contains, in the following order: bid price, bid quantity, ask price, ask quantity

1. Calculate a VwMpt at each timestamp t for each instrument's QUOTES series VwMpt_t = bid_price_t + (ask_price_t-bid_price_t) * (bid_qty_t / (bid_qty_t+ask_qty_t))
2. Calculate a rolling correlation rho of VwMpt returns (first difference, i.e. derivative) sampled at 1 minute intervals with a lookback of 100 samples
3. On a webpage, display a plot of VwMpt substracted from the first sample (so the time series starts at 0) of both series on the same line chart, and below it plot the rho lined up along the same time axis. You may use a library like Flot or something similar.

To download a series with a series_id of FVQUOTES from a Bashoop instance located at 149.202.47.189:8080 you can: curl -s -d "series_id=FVQUOTES" -d "start_ts=0" -d "end_ts=1451606400000000" -d "compress=0" http://149.202.47.189:8080/series -X GET where start_ts and end_ts are micros send epoch. In this case we want the full history.

Answer 29

Parse default arguments

code-golf

Many languages have the concept of default/variable arguments. It basically means you can have a function that when given too few arguments, will fill in the missing arguments with specified values. For example, you can do the following in Python:

WARNING: THE BELOW EXAMPLE CODE IS NOT GOLFED. PROCEED AT YOUR OWN PERIL

def f(x="default string"):
  print x

This means that calling f("foo") will print "foo", but calling f() will print "default string".

Python also has a mechanism for handling too many arguments ("rest"):

def f(*stuff):
  for thing in stuff:
    print thing

You can of course also mix these:

def f(x, y="default string", *z):
  ...

Unfortunately, python (pre-3.5), being python, yells at you when you put a default argument before a non-default argument. That's silly. You guys are smart; you should be able to make that work.

Challenge

Write a program, function, or whatever that when given a string representing the arguments and values passed to them, will print each argument's resulting value.

• If there are too few arguments, the mandatory arguments should be applied first, then the rest of the values into the default arguments (left-to-right).
• If there are too many, apply all values to arguments, and the remaining into the "rest" argument.

I'm even confusing myself, just look at the test cases

Input

• a string, array, or other reasonable format representing the parameter declaration
• a string, array, or other reasonable format representing the values passed to the arguments

Output

• the resulting values of all the arguments, in a reasonable format.
  note: "reasonable format" will be defined later

Test Cases

Test cases will be in the following format:

{arg string}
{value string}
=> {output}

So, here they are

x, y, z
10, 2, 4
=> x:10, y:2, z:4

x=2, y
5
=> x:2, y:5

a, b="a", c, *d
3, 4
=> a:3, b:"a", c:4, d:[]

foo, bar=2, *baz
9, 3, "kqly", 5
=> foo:9, bar:3, baz:["kqly",5]

*x, y
"ha", 2, 3
=> x:["ha",2], y:3

Answer 30

Is this number random?: Round 2

The same as Is this number random?, but with 256 or 512 numbers in each category instead of 64; thereby making a modulo-chain infeasible to find. I hope this will encourage more interesting strategies.

---

Is this enough of a difference from the existing question to merit a new one? Are there any other flaws with the distribution? Could I change this to require splitting into 4 or so buckets instead of 2?