Sandbox for Proposed Challenges

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Answer 1

I Got All Night

---

Meta

• Is this interesting?
• Has this already been submitted?
• Issues/loopholes in the rules?
• Suitable tags?

The goal

Make a program that takes as much time as possible to complete. That's it.

Rules

• It must not be infinite. while(1){} will not be accepted.
• You must be able to show how long it will take. Either through calculating it or by measuring it.
• It must be doing something non-trivial. for(var x=0; x<1000000000000; x++){y++;} will not be accepted.

Scoring

Your score is the time it takes to complete in milliseconds divided by the size of the program in bytes. Round to the nearest point if needed.

For example, if your program is 95 bytes long and takes 3 hours to complete, your score is (3*60*60*1000)/95 = 113,684 (rounded)

---

code-golfbusy-beaver

Answer 2

Help me play Battleship! array-manipulation code-golf grid

Battleship is a two-player guessing game in which each player guesses the placement of the opponent's ships, placed on a grid.

Each column is labeled with a letter, and each row with a number. The label starts from top left (A and 1), and descends as you move right/down.

Each player is given two grids, one for placing ships, and one for guessing the enemy's ship placement. Each player places 5 ships -- one ship of length 5, one ship of length 4, two ships of length 3, and one ship of length 2 -- on her grid, either horizontally or vertically. The players should not share their ship placements.

After placing all ships, each player takes turn guessing the opponent's ship placements. The guessing player guesses one position, and the defending player must announce "hit" or "miss," depending on whether she (the defending player) had a ship there. When all positions of a ship is hit, it is "sunk."

The player who sinks all of the opponent's ships win.

This is an example of a battleship board (taken from Wikipedia):

Task

Given the list of guesses a player has made, construct a 10x10 array that represents the board.

Rules

• The input can take any reasonable format, as long as it is explained. Some examples are [[position, result], [position, result], ...] and [[hit positions], [miss positions]].
• The output array can have any characters, as long as empty, "hit," and "miss" squares are distinguishable from one another. (e.g. unknown = 0, hit = 1, miss = 2)
• You may not take the list of unknown grid positions in the input.

Test Cases

Pastebin link

Sandbox

• Is this challenge interesting?
• Are there any dupes? (I couldn't find one)
• Did I include too much detail in the introduction? (If so, what should I remove?)
• Are my test cases sufficient?

Answer 3

Star Trekkin'

code-golf ascii-art animation

Just an idea at this stage; wanted to get it down lest I forget it. I'll come back to it in a few days to work out the details.

Challenge

Generate an ASCII art representation of the USS Enterprise with an animated, randomised ASCII starfield behind it.

Answer 4

Programming Challenge: Winning criterion is the shortest byte program which can tell me (x, y) which number "x" was doubled in the list, and which number "y" was removed from the list of 1000 numbers from 1 to 1000.

Given a list of 1000 positive integers in random order, find the integer that is repeated more than once, the integers that are not present in the range [1,1000] and output the count of the repeated integer present in the list.

The format of the list is a space deliminated text file such as this:

779 990 5 814 353
627 173 797 714 619
802 719 895 966 325
275 158 322 215 271
631 232 175 10 397
892 124 26 287 878
757 754 508 871 255
363 159 482 400 247
223 857 862 18 434
919 335 586 65 579
828 943 366 874 999
238 289 362 600 321
193 863 613 930 143
107 879 530 284 110
437 426 981 546 924
701 441 941 43 614
542 727 694 351 643
794 563 476 834 624
804 634 776 672 57
597 338 748 908 156
297 234 444 598 891
925 163 229 791 326
944 182 262 987 734
582 910 567 132 28
645 962 994 6 917
617 64 106 304 404
88 93 849 882 677
749 254 12 399 897
329 988 31 379 654
25 646 134 445 327
577 848 673 551 408
405 806 244 40 601
497 177 972 526 545
796 755 630 663 423
428 562 610 1 686
548 281 101 154 747
763 32 236 368 956
639 522 507 792 771
693 147 728 203 845
615 889 931 440 299
348 707 235 320 295
803 513 703 940 717
205 150 702 189 183
296 875 575 454 492
194 425 126 657 976
570 809 945 825 168
890 217 656 29 550
684 188 78 221 446
523 952 676 900 583
484 933 268 608 708
665 17 963 212 253
432 964 858 909 316
155 120 114 210 477
319 647 822 409 388
818 308 77 102 373
929 113 402 841 213
470 877 648 968 135
309 824 690 844 463
323 240 706 391 653
372 985 346 788 510
991 554 494 44 915
758 756 989 759 659
534 142 939 675 378
974 345 462 54 942
681 1000 7 716 415
42 264 996 438 464
386 350 197 141 84
123 127 811 853 516
60 49 277 70 986
98 733 905 978 103
390 230 501 449 731
34 370 541 958 466
251 71 108 846 260
576 830 100 140 529
869 333 303 664 589
856 777 427 187 184
305 766 829 136 456
786 401 737 961 475
412 887 178 91 698
448 433 62 519 832
314 957 861 898 683
983 515 893 220 817
979 149 267 3 63
458 473 139 970 835
666 119 967 695 343
242 947 41 47 623
973 53 354 74 816
121 471 151 246 369
499 45 593 691 376
111 46 226 83 431
274 606 506 265 753
79 387 451 883 525
479 744 162 949 8
292 95 97 324 823
315 152 394 671 718
347 836 50 195 360
812 566 725 612 923
537 911 620 51 328
243 19 556 592 288
334 298 873 655 443
705 66 767 604 285
760 896 474 406 73
918 688 667 914 730
729 826 959 774 543
594 192 27 948 912
491 419 341 518 55
146 787 495 904 172
469 761 840 626 637
144 616 465 712 660
785 365 250 636 384
208 2 174 864 839
741 410 621 342 442
245 568 998 485 216
960 224 239 782 855
291 355 860 807 936
920 56 669 561 697
112 270 715 913 938
364 851 467 751 468
450 995 609 490 72
674 713 640 185 801
361 742 38 784 167
225 743 692 790 907
859 762 569 115 521
116 200 580 632 997
85 82 249 207 486
218 196 14 932 867
429 258 125 793 69
865 385 902 222 531
611 658 318 935 980
808 23 105 722 300
520 30 420 286 662
227 581 745 585 928
330 638 358 587 16
452 635 736 489 252
89 951 137 591 721
880 555 204 535 769
9 820 605 854 148
128 934 396 480 307
161 711 750 704 651
696 133 813 789 517
263 775 553 75 992
293 190 916 273 602
461 11 977 202 764
483 76 52 773 723
870 872 498 359 868
67 544 504 279 833
599 48 171 687 80
547 336 417 642 181
558 906 256 219 81
866 810 709 186 668
572 145 209 739 682
847 752 720 332 393
770 965 574 629 176
746 306 138 798 15
528 778 392 457 726
337 39 86 380 160
493 211 436 180 241
795 94 955 837 214
584 954 117 549 59
340 805 367 927 633
946 738 819 487 557
768 4 37 827 596
511 628 381 68 679
838 179 603 680 13
231 650 35 700 735
975 595 502 301 424
527 678 950 280 532
649 685 710 539 903
248 276 571 500 435
560 109 926 588 278
414 509 237 169 740
885 118 430 382 689
481 311 199 993 821
261 447 540 357 92
129 131 953 375 377
852 61 191 228 937
122 418 439 573 198
331 302 505 644 283
421 416 36 894 884
831 22 24 104 876
371 272 622 312 578
459 395 455 536 374
969 403 565 269 389
552 90 164 922 781
503 460 524 206 356
130 259 533 294 157
901 422 290 514 982
641 661 478 559 496
282 512 266 257 538
765 564 96 783 724
843 317 411 799 652
488 310 349 313 413
453 886 58 971 20
921 618 815 850 99
339 87 21 472 699
33 607 800 352 899
233 166 780 407 625
670 201 170 383 772
344 376 881 984 590
165 732 153 398 842  

For example in this list 376 is repeated twice, and 888 is removed once. In this challenge a number "x" can only be repeated "once", so the number "888" can only be removed once, so an acceptable output for a programmed answer is this "(x, y)" where "x" is the number repeated twice, and "y" is the number removed.

I attempted to make this programming question, but because I included a bonus for web-scraping, and the format of the output for an answer was not clear it didn't receive positive reviews.

So I would like suggestions I how I can make this challenge clearer. Thank you.

Here is my challenge and the comments I received.

Programming Challenge: Tell me which number I repeated, how many times, and which one I skipped?

Answer 5

Working For The Weekend

code-golf date

Option 1

Taking no input, output true if today is Saturday or Sunday or false otherwise.

---

Option 2

Taking no input, output how many days, from today, until the weekend.

Sunday:    0
Monday:    5
Tuesday:   4
Wednesday: 3
Thursday:  2
Friday:    1
Saturday:  0

---

Sandbox

• Which option do you prefer?
• Too trivial?
• Dupe?
• Allow local times to be used or require UTC? (I wanna say UTC)
• true & false or truthy & falsey? (if option 1)
• Working or Livin' For The Weekend?

Answer 6

What could I add to improve this post? I have some questions that are inside of brackets.

Introduction

A farmer needs help calculating the least time it will take him to pick his fruit each day.

Challenge

• This farmer has X orchards.
• Each orchard has Y [is Y the correct variable to use here? does it matter?] fruits in it. If the orchard has no fruits, then it will contain the string "none".
• The farmer has a list, this list contains the fruit he must pick.
• The farmer will only go down the list in order
• You must calculate how long it will take the farmer to pick his fruit on each day.

More on the orchards

• All of the orchards are in a line.
• Each orchard is exactly 1 unit [should I say unit or kilometer?] away from the next and previous one.
• The farmer can go up and down the line, but may not jump from one orchard to another

Input and Output

You will receive an input in the following format:

X
*string*
*string*
*string* *string* *string* *string*
*string*
//ect.
Y
*string* *string*
*string* *string*
*string* *string*
*string* *string*
//ect.

X is the number of orchards

• Everything after X and before Y is an orchard containing a/some string(s), each string is a different fruit in that orchard.

Y is the number of days that the farmer must gather fruit.

• Each day consists of two strings that are different fruits.
• You must find what orchard these strings are in and calculate the difference.

Input Rules:

1. Each fruit name string will be one word with no spaces
2. [Should I add more here? if so, what should I add?]

Real Example

Still confused? Maybe this will clear it up:

Input

6 

none

apple

orange pear pear

none

orange lemon pumpkin

pumpkin lettuce flowers peas

4

peas lettuce 

apple orange 

apple pumpkin 

flowers orange 

output: [ 0, 1, 3, 1 ]

Explanation

Input:

• 6 the number of orchards
• A set of 6 orchards containing fruit, each orchard on a new line.
• 4 the number of days on the farmers list.
• A set of 4 fruits to compare, each pair of fruits is on a new line.

Output:

• Output an array of the differences between each set of fruits.
• The difference between peas and lettuce is 0, because they are in the same orchard.
• The difference between apples and oranges is 1 because they are one orchard apart.
• The difference between apples and pumpkins is 3 Because they are three orchards apart.
• The difference between flowers and oranges is 1 because they are one orchard apart.

---

Annotated input/output

6 orchards 

a none

b apple

c orange pear pear

d none

e orange lemon pumpkin

f pumpkin lettuce flowers peas

--

4 fruits

peas lettuce 0

apple orange 1

apple pumpkin 3

flower orange 1

--

output: [ 0, 1, 3, 1 ]

Answer 7

Studio 54

code-golf decision-problem number

Studio 54 was a famous nightclub in Manhattan. The club is referenced in the Futurama episode Rebirth in which the crew visits a nightclub called Studio 1²2¹3³. The mathematical expression 1²2¹3³ evaluates to (1 x 1) x (2) x (3 x 3 x 3) = 1 x 2 x 27 = 54.

Challenge

Determine whether a positive integer is a "studio number." We define a studio number to be a number n that can be expressed as the product of a set of distinct positive integers that does not include n, each of which is raised to the power of one of the numbers in the set. Or, more mathematically:

You should have a consistent output value for "is a studio number" and "is not a studio number," and nothing else.

Test cases

These are inexhaustive lists and are just meant for basic ad-hoc testing.

Studio numbers:

4
12
16
18
52
54
64
68
72
88
96

Not studio numbers:

1
2
9
10
11
42
53
55
69
77
87
90

Computed by this script.

Sandbox

I'm going off of this for the two consistent outputs, but I'm not really sold either way. I could also change the requirements to be to output the "studio" representation of the number.

Does the math-y bit help? Could I make the studio number definition clearer?

I've been unable to find any "nice" properties of these numbers that allow for methods besides brute force. Would this still be interesting enough to golf? I could also add a "reasonable time" limit that would enforce some non-naive code to reject bad attempts, but I'm not sure that's much better.

The studio numbers do not appear to be a sequence recorded on the OEIS.

Answer 8

Only HeLlO WoRLd is allowed.

We are all familiar that "Hello World" is the 1st introductory program that most people learn when they first start to program. Then programmers go on to greater and better programs. But who says they have to go on to greater and better programs? What if all other programs were censored?

Your Task:

Write a computer program that takes in standard input. If the standard input is any case-insensitive version of HeLlO WoRLd, do nothing. If the Standard input is anything other than a case insensitive HeLlO WoRLd, print an infinite loop of a HELLO WORLD matrix to the standard output.

To print an infinite HELLO-WORLD-Matrix, randomly sort the letters of "HELLO" and the letters of "WORLD", join the two words with a space as if you were saying HELLO WORLD, although you are probably saying "HELLO DWROL", " OELLH LWODR" gibberish with an occasional "HELLO WORLD". Then just keep printing all this gibberish to the standard output.

ELHOL WRDLO     HOELL LDWRO     LOELH DLWRO     EOLHL DRLOW     LHELO OLRWD     

OLELH LODRW     EOHLL LWROD     LLOHE OWDRL     HLLEO OLRWD     LEHOL LOWDR  

OLLHE WROLD     OLEHL DLRWO     OHLEL OWDLR     LLHEO OWDRL     LLEHO ROLWD     

HELOL WLORD     HLOLE LWODR     LHOEL ODLWR     OLEHL DWORL     LLHEO OWDRL     

LHOLE WORDL     LOLHE WLODR     HLLOE WRODL     HOLLE LDORW     EOLHL WODLR  

ELOHL DRWLO     LHELO LRDWO     HLOEL RLDWO     LHOLE DOWLR     OLELH DOLWR     

OLLEH WORLD     LHLOE RWLDO     OELLH LWODR     LEHLO DOLRW     EOHLL DWRLO     

HELLO WORLD     LOLEH ODWRL     HOLLE WDLOR     LHEOL LORWD     LLOHE OLDWR     

OHLLE DRLOW     LOEHL LODWR     OHLLE ODRLW     HOLEL LWDRO     HOLEL DWROL  

ELOLH RWOLD     EOLHL WDLOR     LHOLE WRODL     HLLEO ODLRW     HLELO LDWOR     

HLELO WLDRO     HLLOE DRWLO     HOLEL OLWRD     OELHL WORDL     HOELL LDRWO     

LLEHO WORLD     OLELH DLOWR     OLHEL LDWRO     ELOLH DWROL     EHLLO WDLRO  

OLELH LDROW     LHEOL WORLD     OLEHL LWDRO     OELHL RWLOD     LEOLH RWOLD     

HLOLE DRLOW     LOELH RWLOD     LHELO LODWR     LLOHE LWDRO     LOEHL OWDLR     

LEHOL WORDL     OLEHL RWLDO     LOELH LOWDR     HEOLL LODRW     HLOLE RLODW  

LLEHO DWORL     LLOHE DWOLR     LLHEO RODWL     OLLEH DLWOR     LHEOL ORDWL     

HLEOL OWDRL     LELOH LDROW     HELLO LDWRO     HOELL ODWLR     OEHLL ROWDL     

EHOLL WRLDO     HLOLE WRLDO     LLHEO WDRLO     LOLEH OLDWR     OEHLL RLWDO  

OELHL DLORW     LLHEO RDWOL     HLLOE OLDRW     OLLHE LRODW     OELLH LDROW     

LEHOL LOWDR     LEHLO DRLOW     HOLEL WROLD     LHELO LORWD     EHLLO LWODR     

HLOLE OLRDW     LOLHE OLRWD     LOLHE DORWL     LOHEL WDLRO     OHELL RWOLD  

LEHLO RLWDO     HLEOL LWRDO     OELLH LWORD     HELLO LDROW     OLHLE LWDRO 

 

There is actually only one "HELLO WORLD" amid all this gibberish

Winning criterion: shortest program in bytes.

Answer 9

Golfing a Busy Turing Machine

code-golf turing-machine busy-beaver

For the sandbox

This question is really hard, and the solution is restricted to one "language" – a 1-tape, 2-symbol Turing Machine. So I'm not sure if it belongs on PPCG. I've written up a basic description below, but can go into more detail if anyone is interested.

Question

I recently came across a paper that explicitly presents a 7910-state 1-tape, 2-symbol Turing machine that cannot be proven to run forever in ZFC, assuming ZFC is consistent. It also cites codegolf.stackexchange.com!

The existence of this Turing machine proves that calculating BB(7910) is independent of ZFC.

So, we know that we can calculate up to at least BB(4), and definitely can't calculate BB(7910) and above.

Can you create a Turing Machine with under 7910 states that cannot be proven to run forever in ZFC?

The author designed two custom-purpose programming languages (Laconic and TMD) to create this Turing Machine. In order to improve upon his work, I imagine you could go one of three ways:

1. Optimize his algorithm in Laconic such that it encodes the interpreter or Friedman's mathematical statement (section 3.1) more tersely.

2. Optimize TMD so individual instructions are translated to fewer states.

3. Find a simpler statement whose truth implies the consistency of ZFC, and encode that instead of Friedman's statement.

4. Go another direction entirely!

Winning criteria

The Turing Machine with the fewest number of states that cannot be proven to run forever in ZFC, wins. The length of the code you used to generate this Turing Machine is irrelevant.

You don't win if you compute BB(5), but you do get eternal fame.

Answer 10

Grouped Keyboard Scores

code-challenge

In the above graphic, one can see 12 distinct color groups, which roughly correspond to columns on a keyboard. The following is a plaintext representation of which characters occur in each group.

Group 1:  ~` \n\t
Group 2:  !1QqAaZz
Group 3:  @2WwSsXx
Group 4:  #3EeDdCc
Group 5:  $4RrFfVv
Group 6:  %5TtGgBb
Group 7:  ^6YyHhNn
Group 8:  &7UuJjMm
Group 9:  *8IiKk<,
Group 10: (9OoLl>.
Group 11: )0Pp:;?/
Group 12: _-{["'+=}]|\

Challenge: Sort characters in the input according to their position in the aforementioned table. For input "Hello, World!", the output would be " !WedrH,llool". The relative order of characters within the same group does not matter, so the output " !WderH,llloo" is just as acceptable.

Scoring: Let P be the product of the number of characters in each non-empty section. Let S be the number of sections your program uses. Then, your score is P × S.

For example, the program QAZ would have a score of 3, and QWERTY would have a score of 6. 12321 would have a score of 12. The lowest such score wins.

Here is a code snippet for scoring your submission:

var sections = [
    "`~\t\n ",
    "!1QqAaZz",
    "@2WwSsXx",
    "#3EeDdCc",
    "$4RrFfVv",
    "%5TtGgBb",
    "^6YyHhNn",
    "&7UuJjMm",
    "*8IiKk<,",
    "(9OoLl>.",
    ")0Pp:;?/",
    "_-{[\"'+=}]|\\"
];

function getSection(chr){
    for(var i = 0; i < sections.length; i++){
        if(sections[i].indexOf(chr) >= 0){
            return i;
        }
    }
    return -1;
}

function score(program){
    // group by sections
    var sectionHolder = [];
    var foundSections = [];
    for(var i = 0; i < program.length; i++){
        var chr = program[i];
        var index = getSection(chr);
        if(index < 0)
            return "n/a\nInvalid character: " + chr;
        
        if(!sectionHolder[index])
            sectionHolder[index] = [];
        
        sectionHolder[index].push(chr);
        
        if(foundSections.indexOf(index) < 0)
            foundSections.push(index);
    }
    
    var S = foundSections.length;
    var P = foundSections.map(function(e){
        return sectionHolder[e].length;
    }).reduce(function(a, c){
        return a * c;
    }, 1);;
    
    return S * P;
}
var output, code;
window.addEventListener("load", function(){
    output = document.getElementById("output");
    code = document.getElementById("code");
});
function update(){
    output.innerHTML = "";
    output.appendChild(document.createTextNode(
        "Score = " + score(code.value)
    ));
}

* { font-family: Consolas, monospace; }
#output { white-space: pre; }

<textarea id="code" oninput="update();"></textarea>

<div id="output"></div>

Test cases

Note: ␉ represents a tab and ␤ represents a newline.

 "input" => "output"

 "Hello, World!" => " !WedrH,llool"
 "Grouped Keyboard Scoring" => "  aSededcrrrGbgynuKiooop"
 "QWERTYUIOPqwertyuiop" => "QqWwEeRrTtYyUuIiOoPp"
 "2017 + 42 = something" => "    122se4tghn7mio0+="
 "Tab␉ulator" => "␉aarTbtulo"
 "Hello␤World" => "␤WedrHllool"

Answer 11

Call a library function

Given a single int32, a path to a Dynamic Link Library (.dll) or Shared Library (.so), and the name of a function, return the single int32 result of calling the function on the single int32.

Examples

On 64 bit Linux: 0 /usr/lib64/libm-2.24.so fesetround → 0

On 64 bit Linux: 1 /usr/lib64/libm-2.24.so fesetround → 1

On 32 bit Linux: 1023 /usr/lib/libm-2.24.so fesetround → 1

On 32 bit Linux: 1024 /usr/lib/libm-2.24.so fesetround → 0

On 64 bit Windows: inp please\edit\filename.dll fname → out

On 64 bit Windows: inp please\edit\filename.dll fname → out

Answer 12

What is the maximum number of backslashes (escape characters) required to mean one backslash?

If you want to use a regex to look for a backslash, you have to escape that backslash, so that the character after it isn't escaped instead. But if you then have to store this regex in a string (in a c-style language, for instance), you need to double the number of backslashes, so that a regex string to match \stuff\ would need to be "\\\\stu(f+)\\\\" (and I had to further double the backslashes to post it in StackOverflow, but that isn't executable so doesn't count).

In your answer, explain the language and the (reasonable) situation, from either real or made-up business needs, and the answer with the most backslashes (per final, output backslash) will get upvoted (permanently) and accepted (until a better one comes along). If using AutoHotKey or another language that has a different escape character (for instance, `), then instances of that character will count instead of backslashes.

This question is not how many backslashes could you use in some esoteric code-golfing language to eventually calculate to a backslash, otherwise I don't think there would be an upper limit. This instead is about feasible scenarios that force you to use a lot of backslashes.

Answer 13

Write an interpreter for XKCD's broken language

code-golfinterpretercode-challenge

---

Meta

• Is this a good idea?
• Is the point system good?
  • If so, are the point values good? I based them off of how difficult I imaged each part to be.

Overview

Randall Munroe, author of the webcomic XKCD, posted a comic a while back about a joke programming language and how it gets types confused.

Here's the comic in question

Your job is to write an interpreter for a slightly modified version of this language.

Rules

• If your language supports it, it must be a live interpreter where all input lines start with [#]> (where # is the line number) and all outputs must start with =>.
  • If your language does not support it, you may substitute this with reading all the lines on the input and printing out each output on its own line, still starting with =>. Remember to keep track of line numbers.
• All commands must be usable in any order and with any parameters (within reason)
• Each command you implement correctly is worth the listed point value. See scoring to find your final score.

Integers plus numeric strings (1 point)

Given an int and a string containing a number (in that order) calculate the numeric sum of them, then return the result as a string with quotes surrounding it.

[1]> 2 + "2"
=> "4"
[2]> 6 + "13"
=> "19"

Numeric strings plus lists (1 point)

Given a numeric string and a list, append the numeric value to the list and return the list as a string.

[1]> "3" + []
=> "[3]"
[2]> "7" + [1,4]
=> "[1,4,7]"

Dividing by zero (1 point)

Any number divided by zero returns a NaN object. This does not have quotes around it.

[1]> 1/0
=> NaN

NaN plus integer (2 points)

Given a NaN object and an integer, pretend it's a string and increment the leading character, carrying over if needed. The result does not have quotes.

[1]> (5/0)+2
=> NaP
[2]> NaN+256
=> NbN

You do not need to use ASCII for this, any character set works, as long as it includes at minimum the 52 uppercase and lowercase letters.

You will never have to add a result from this to another integer. (For example, NaP+4 is invalid)

String plus string (1 point)

Given two strings, remove swap the first and last quotes with single quotes and return the result.

[1]> ""+""
=> '"+"'
[2]> "Hello"+"world"
=> 'Hello"+"world'

List of integers plus integer (3 points)

Given a list of integers (or an empty list) and another integer, return True or False based on whether the new integer matches the linear pattern.

It will follow this rule:

If the list has 0 or 1 items, return True regardless (everything matches).
Determine the pattern of the list by subtracting every item by the item right before it. If the pattern is inconsistent, return False regardless (nothing matches).
Otherwise, check if the new integer matches the pattern. If it does, return True. If it doesn't, return False.

[1]> [1, 2, 3, 4] + 5
=> True
[2]> [5, 7, 9, 11] + 13
=> True
[3]> [6, 5, 4, 3] + 2
=> True
[4]> [2, 4, 6, 8] + 9
=> False
[5]> [1, 2, 1, 4] + 5
=> False

Range(a, b) (1 point)

With the Range function given two numbers, return a list of numbers from a to b.

[1]> Range(1, 5)
=> [1, 2, 3, 4, 5]
[2]> Range(3, 6)
=> [3, 4, 5, 6]
[3]> Range(6, 4)
=> [6, 5, 4]

Plus integer (1 point)

Given simply "+" and an integer, return the line number plus the integer.

[1]> +2
=> 3
[2]> +2
=> 4
[3]> +1
=> 4

Single digit plus single digit (2 points)

Given two single digit integers a and b, replace all future instances of a in the output with (a+b)%10 (where % means modulo, essentially wrap around if the result is more than 1 digit). Return Done. This effect is superficial and has no effect on math. This only affects output, not input.

[1]> 3+2
=> Done
[2]> Range(1, 6)
=> [1, 2, 5, 4, 5, 6]
[5]> 1+2
=> Done
[4]> Range(1, 6)
=> [3, 2, 5, 4, 5, 6]

Floor (1 point)

Draw an ascii art floor with the number at the bottom. The specifications are 3 lines of only pipes, then a line with a pipe, 3 underscores, the number, and 3 underscores.

[1]> Floor(4.7)
=> |
=> |
=> |
=> |___4.7___
[2]> Floor(105.3)
=> |
=> |
=> |
=> |___105.3___

Scoring

Add up the points you've earned. Your score is now calculated as (15-points) * bytecount. Lower is better.

Notes

• You do not have to account for mixing functions. For example, Range(Floor(2.3)) is invalid.
• Whitespace may be added or removed as is convenient.
• Double quotes or single quotes may be used as convenient (as long as you use the opposite for "String plus string")
• Any brackets may be used for lists, as long as it's consistent.
• A few commands were omitted from the original comic because I couldn't figure out a way to make it well specified.

Answer 14

Counting from 0 - 100

I posted this question, but it was not taken very well, so I wanted to put it through the sandbox and get some feedback/help before re-posting.

Challenge

Output all numbers from 0-100. Without using any of your languages built in loops.

Loops that are not allowed

This list contains, but is not limited to

• For loops
• While loops
• Do While loops
• Goto Statment
• In Range

Rules

• This is code-golf the shortest solution in bytes wins
• Standard Loopholes Apply
• You may use functions as well as programs

Answer 15

OCR

test-battery code-challenge

In this challenge you will attempt to write a program to perform OCR in the fewest bytes possible. The tests are linked below, the only data that your program receives is the contents of the image, you may not rely on file name, timestamp, or other metadata, additionally you may not query any external source such as the internet or dispatch an independent program to outsource the task of OCR.

Spec

Given a hand written word in in image of 80px in height. Output the word. words will consist of lowercase latin letters:

abcdefghijklmnopqrstuvwxyz

Scoring

Given the test cases, your score is a percent of the words you have gotten correct. No partial credit.

---

Tests cases:

TODO

Answer 16

Data exfiltration

Frenzy in the frequency domain.

Summary of the challenge

You must find a way to broadcast a ten-character password through a lossy communication channel and recover the password on the other side. To achieve this you must write two programs. The first program will receive the password as input and encode it as output data for the channel, the second program has to decode the output of the channel back to the password.

Some background

In signal processing theory, many problems are usually dealt with by converting a signal from the time domain to the so-called frequency domain, a trick that relies on the fact that any function can be written as an infinite series of sine waves. Signals can be converted into this domain using a Fourier transform. This transform is lossless, and the resulting signal can be converted back into the time domain using the inverse Fourier transform. The frequency domain has some interesting properties, as the actual values of the signal in it represent the amplitude and phase of different frequencies in the original signal.

A special case exists for when the signal exists out of equally spaced sampled points, called the discrete-time Fourier transform. To perform this transform the fast fourier transform algorithm is commonly used. Given a signal of N samples spaced with dt spacing, it will convert it into a signal containing N frequency bins which are each 1/(N*dt) apart.

Channel definition

The communication channel requires 256 unsigned bytes data as input, and returns 256 unsigned bytes data as output. If the input values are centered around zero and interpreted as data samples on regular intervals, then the output values represent the amplitude of the signal in the frequency domain scaled to use the range 0 to 255, calculated using a discrete fourier transform. The channel is lossy as it only transfers the amplitude of each frequency, not the phase.

It can be simulated using the following python 3 script:

import cmath
def channel():
    # amount of input and output values
    l=256
    # read the input values from standard input as newline separated integers and center them around zero
    n=list(map(lambda: min(255, max(0, int(raw_input())))-127.5, range(l)))
    # perform a discrete fourier transform
    v=[sum(v*cmath.exp(-2.0j*cmath.pi*t*k/l)for t,v in enumerate(n))/l for k in range(l)]
    # remove artifacts due to the Nyquist limit
    v[1:128]=map(lambda n:n*2,v[1:128])
    v[129:]=[.0]*127
    # return the scaled magnitude of each frequency bin
    for i in v:print(int(round(abs(i)*cmath.pi/2)))

Input/Output

The password is randomly generated using only using visible ASCII characters (0x20 up to and including 0x7E) and is 10 characters long.

Inputting the password to the encoder, communicating it to the channel, receiving data from the channel and communicating the decoded password should all follow the default input/output rules. The password must be decoded only from data received from the channel, no side-channels are allowed.

Scoring

This is code-golf, where the score is calculated by adding the length of both the encoder and decoder program. For each language, the shortest entry in bytes wins.

Meta

• Is the challenge clear
• Is the difficulty okay
• Anything else?

Tags: code-golf

Answer 17

List My Factors!

code-golfmath

---

Introduction

Given an algebraic expression as input, list all the factors of it. A factor of an algebraic expression is any algebraic expression (or simply a numerical expression, sometimes) that evenly divides it. A factor can only be an integer or an algebraic expression consisting of integers and variables.

---

Rules

• The algebraic expression will contain * to denote multiplication.

• The algebraic expression will only contain integer constants and coefficients.

• The algebraic expression will contain ^ to denote exponentiation.

• The algebraic expression will only contain positive constants, coefficients and variables.

• Your program should output only the positive factors.

• The algebraic expression will not contain negative exponents.

• You must not use any built-in to accomplish this.

• Standard Loopholes apply.

---

Examples

The algebraic expression 5*x^2 has the following factors:

1. 5
2. x
3. x^2
4. 5*x^2
5. 5*x
6. 1

The algebraic expression 10*(x-y)^2 has the following factors:

1. 10
2. 5
3. 2
4. 1
5. (x-y)
6. (x-y)^2 or x^2 + y^2 - 2*x*y
7. 2*(x-y)^2 or 2*(x^2 + y^2 - 2*x*y) or 2*x^2 + 2*y^2 - 4*x*y
8. 5*(x-y)^2 or 5*(x^2 + y^2 - 2*x*y) or 5*x^2 + 5*y^2 - 10*x*y
9. 10*(x-y)^2 or 10*(x^2 + y^2 - 2*x*y) or 10*x^2 + 10*y^2 - 20*x*y.
10. 10*(x-y) or 10*x - 10*y
11. 2*(x-y) or 2*x - 2*y
12. 5*(x-y) or 5*x - 5*y

The algebraic expression x^2 - y^2 has the following factors:

1. 1
2. x-y
3. x+y
4. x^2 - y^2

---

Input

Your program may take the input in any way except assuming it to be present in a predefined variable. Reading from file, input box, modal window, command line etc. is allowed. Taking input as function argument is allowed as well.

---

Output

Your program should output a list of factors of the given input as a collection data type (such as array) or as a separator-separated String.

Your program may output in any way except writing the output to a variable. Writing to file, screen, modal window, command line etc. is allowed. Outputting using function return is allowed as well.

---

Test Cases

Input               Output

5*x^2               [5*x^2, 5, 1, 5*x, x, x^2]
10*x^2              [10*x^2, 10, 5, 2, 1, 10*x, 5*x, 2*x, x, 5*x^2, 2*x^2, x^2]
10*(x-y)^2          [10*(x-y)^2, 10, 2, 5, 1, 10*(x-y), 5*(x-y), 2*(x-y), (x-y), (x-y)^2, 2*(x-y)^2, 5*(x-y)^2]
x^2 - y^2           [x^2 - y^2, x+y, x-y, 1]

---

Winning Criterion

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

---

Sandbox

1. Should I allow negative constants and coefficients? Answer : No
2. Should I allow variable exponents?
3. Is there any mistake in Examples and Test Cases?
4. How long should I let this challenge be here?
5. Any problem with the Input/Output Rules?
6. Should I allow built-in to accomplish the task?
7. Any other suggestion?

Answer 18

Rotational Anagrams

Given, for lack of a better word, an anagram cube c with n rings and a word w, output whether or not you can rotate the individual sections to make w appear across the middle.

Constraints

• The letters that can appear are all printable ASCII characters EXCEPT for newlines.
  • All three characters that make up the rings can appear (|-+).
• Your program should work for cubes of any size, though the maximum I expect you to test is my biggest case (this means that if your code won't finish for n=22 on TIO, I don't care).
• Your only input should be the ASCII-art c and the word w.
• Your only output is one of two distinct values for true/false, which are arbitrary.
• You can assume the input is well-formed, and output anything for bad input.

Examples

Example cube with n=3 and w='AXMOZC':

+----A----+
| +--Y--+ |
| | +N+ | |
B X M O Z D
| | +P+ | |
| +--W--+ |
+----C----+

Rotate the outer wheel once coutner clockwise:

+----D----+
| +--Y--+ |
| | +N+ | |
A X M O Z C
| | +P+ | |
| +--W--+ |
+----B----+

Ding-ding! A match, so we can output truthy for this, but for AXMOYC there is no rotation that allows that combination, so it would return falsy. (X and Y are not adjacent on the ring, which means they can't appear at the same time.

---

Here's a small cube of n=2:

+--G--+
| +P+ |
P C P G
| +C+ |
+--P--+

For an input w=PPCG|GPCP|PCPG|GCPP this returns true, everything else is false. So you can start to see that the possible keyspace of answers is always n**2, so... hint hint.

---

Here's the big honkin' example that took me a minute to piece up.

+----------1----------+
| +--------O--------+ |
| | +------5------+ | |
| | | +----E----+ | | |
| | | | +-----+ | | | |
| | | | | +G+ | | | | |
C 3 D E - B O L L I 4 G
| | | | | +O+ | | | | |
| | | | +--W--+ | | | |
| | | +----F----+ | | |
| | +------6------+ | |
| +--------N--------+ |
+----------2----------+

And, amongst many other strings, for w=CODE-GOLFING|CODE-BOWLING you should return true.

---

This is ascii-artpermutationscode-golfparsing, if you're on my front lawn the third Tuesday of next month in a batman costume doing unspeakable things to my sprinkler system, you've won.

Answer 19

Home on the Range code-golf number

Challenge

Given a range [0,n) that has been shuffled, return the index of each element of the range.

Examples

[1, 2, 0] -> [2, 0, 1]

This is the range [0, 3) after being shuffled. The element at index 0 in the result is 2 because, in the input, 0 is at index 2. Likewise, the 0 in the output is the index of the 1 in the input, and the 1 is the index of 2.

[1, 0, 2] -> [1, 0, 2]
[0, 1, 2, 3] -> [0, 1, 2, 3]
[0, 2, 1, 3] -> [0, 2, 1, 3]
[2, 0, 1, 3] -> [1, 2, 0, 3]
[3, 2, 0, 1] -> [2, 3, 1, 0]
[4, 3, 2, 0, 1] -> [3, 4, 2, 1, 0]
[1, 2, 4, 0, 3] -> [3, 0, 1, 4, 2]
[2, 4, 0, 3, 1] -> [2, 4, 0, 3, 1]

Bonus

I will award a +100 bounty to the first person to design and explain an algorithm that solves this problem using O(n) time and O(1) space.

Sandbox

• I think my explanation was rather poor. How can I make this more clear?
• Is this a dupe?
• Is the bonus a good idea? (I really want to hear the answer because I don't know if this is even possible!)

Answer 20

Find the maximum number of coprimes in a set

Inspired by a recent question on Math.stackexchange.com, which I can't find anymore.

The challenge

Exactly what it says on the tin. You are given a set of integers and you have to create a program (according to the default definitions on meta) that outputs the size of the biggest subset that shares no divisors except for 1.

Input

A set of nonzero positive integers of length >= 2. You can take this input as per the defaults in meta.

Output

Output, print or return the size of the subset of the input that does not share any divisors except for one.

Testcases

1 2 3 4 5 6 7 8 9 10 11 12 13 14
7

1 3
1

2 3 5 7 9
4

2 3 5 7 11 13
6

Answer 21

Golf a program whose behavior is independent from Peano arithmetic

Your task is to write a program that doesn't take any input, and whose termination cannot be proved or disproved inside Peano arithmetic. This is code-golf, so the shortest byte count wins!

Rules

• Standard loopholes apply
• Shortest by count wins
• You can assume that your program runs in a machine with an unlimited amount of memory.

Tags

code-golf busy-beaver

---

Questions for meta

• Is this a good challenge?
• Is it a duplicate?
• I think the same question with a behavior independent of ZF set theory might be interesting as well (see this link for instance), but will attract very different answers; should I post it as a separate challenge?
• What can be improved? Are the tags ok?

Answer 22

Iterate over all sets

(This question needs fixing so that the output size is not too large)

Consider all possible pairs of sets of integers (can have positive, negative and zero values) A and B such that |A| = |B| = 7. Define the set T_{A,B} = {a * b | a in A, B in B}.

The challenge is to iterate over all pairs of sets A and B so that |T_{A,B}| < 19 and the largest absolute value of an integer in A or B is at most 128. As an example of one such pair of sets, A = B = {2^i | for i in {1,...,7}}.

What should my code output?

Your code should output the pairs of sets A, B along with |T_{A,B}|.

For example:

A = {2,4,8,16,32,64,128}, B = {2,4,8,16,32,64,128}, |T_{A,B}| = 13.

Running time

I don't care how long your code takes to run except you must run your answer to completion before posting an answer.

Answer 23

Code golf the Fast growing hierarchy (fgh)

if your not familiar with the fgh you migth want to check out this explantion: Large Numbers, Part 3: Functions and Ordinals

and these value aproximations: Fast growing hierarchy Approximations

the goal this code golf is to golf the following functions:

• the exact value of f_ω(x) this means you can't golf the ackermann function

• the growth rate of f_ω2(x)

• the growth rate of f_ω²(x)

In any language of your chose.

This is a code golf so the smallest program that defines each of these functions wins (Note:the functions are allowed to call each other).

It is also allowed to ask for an input x and output the 3 function values in any order.

Tags

busy-beaver,growth-rate-golf,code-golf,recursion

Sandbox notes

I'm not sure on which functions should be the target but these functions seem challenging yet golf-able in less than 150 bytes.

Upon closer inspection I realized that f_ω²(x) is probably to easy since it can be golfed with something like:

f(x,a...) {
    for i in range(a.length) {
        if(a[i] != 0) { //first non zero
            Arrays.fill(a, 0, i, x); //replace 0's with x
            a[i]--; //decrement a[i]
            return f^x(x,a);
        }
    }
    //all zeros
    return x+1;
}

f(x,n) > f_n(x)

f(x,0,n) > f_ωn(x)

f(x,0,0,n) > f_ω^n(x)

so f(x,0,...,0,x) (x zeros) ~= f_ε0(x)

Any other tags? Suggestions? Does this interest you?

Answer 24

Just One More Time code-golf

Challenge

Write a program or function that will run without error once, but will crash when run for the second time.

If you are writing a function, you may assume the function will be run twice within the same interpreter session or program.

If you are writing a program, you may assume the machine will not be rebooted between runs.

Scoring

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

Answer 25

What Tiles did I have?

Everyone should be aware of the scoring system in a classic board game: Scrabble. I remember going back into my old scrabble box and finding some old post-it notes containing old scores. I always wonder what the heck was played for some of the more insane point scores. That gave me the idea for this challenge...

---

English-language editions of Scrabble contain 100 letter tiles, in the following distribution:

• 0 points: * x 2 (These are the blank tiles)
• 1 point: E ×12, A ×9, I ×9, O ×8, N ×6, R ×6, T ×6, L ×4, S ×4, U ×4
• 2 points: D ×4, G ×3
• 3 points: B ×2, C ×2, M ×2, P ×2
• 4 points: F ×2, H ×2, V ×2, W ×2, Y ×2
• 5 points: K ×1
• 8 points: J ×1, X ×1
• 10 points: Q ×1, Z ×1

---

Your challenge is, given a single integer input between 0 and 185, output a corresponding sequence of scrabble tiles that sum to that score with a length between 2 and 100 characters in length.

The Specifics

• The letters don't have to spell anything, they just have to sum to that score.
• You can only use a tile the number of times it exists (E.G. E can be used 12 times).
• The shortest word is 2 characters long, for an input of 0 you get **.
• Outputs will not match between answers, as there are many solutions.

Inputs and Outputs

• Input should be a single integer, anything else is wrong.
• Output should be a single string, with no spaces, order of letters is arbitrary.

Example (Potential Solution)

0   | **
1   | *E
2   | EE
[... Pattern Omitted ...]
12  | EEEEEEEEEEE
13  | EEEEEEEEEEEA
[... Pattern Omitted ...]
68  | EEEEEEEEEEEEAAAAAAAAAIIIIIIIIIOOOOOOOONNNNNNRRRRRRRTTTTTTLLLLSSSSUUUU
[... Arbitrary Ordering Omitted ...]
185 | EEEEEEEEEEEEAAAAAAAAAIIIIIIIIIOOOOOOOONNNNNNRRRRRRRTTTTTTLLLLSSSSUUUUDDDDGGGBBCCMMPPFFHHVVWWYYKJXZQ

---

This is code-golf,strings: Whomever contacts Cthulhu using the dark arts first wins.

Answer 26

Display the Undisplayable

I have sometimes seen answers to challenges, written in binary machine code. The users who post them usually display them in hexadecimal representation. This representation makes the code extremely long, and does not do them justice!

Thus, we should give them help, and I don't care if they don't need it. Your task will to write a program/function/eldritch incantation to turn their beautifully golfed binary code into the shortest possible string of printable characters.

Input

A sequence of random binary data of random length. Use any of the standard IO methods (note to self: find the link to the Meta post).

Output

A sequence of printable characters. Use any of the standard IO methods.

• If encoding is relevant, you are free to choose any encoding, provided you clearly indicate which one you used in your answer. What is relevant is the number of characters anyway.

• Whitespaces (regular space, new line, non-breaking space, form feed, etc.) are considered not printable. They can be added if you wish, but their presence or absence must not impact the decoding of the output.

Conditions

• There must exist a program, that can take any possible output of your program, and turn it back into the input (providing it is not needed, but will be smiley'd at).

• If your program is run twice, with 2 inputs of same size, the 2 resulting outputs must have the same size.

• Standard loopholes apply.

Score

The score is calcaulated as the number of bytes in the input, divided by the number of characters in the output. The higher the better.

If the score varies depending on the length of the input, take its average over input sizes from 1 to 1024 bytes included (I don't think we'll have answer 1 kb long here).

---

Giving an answer in a binary language (machine code, LLVM bitcode, etc.) and adding the output when run with its own binary source will be smiley'd at (but no bonus, unless it can also summon Cthulhu).

Don't forget to explain how your code works!

---

Meta

• Do you think it's a good idea? Is there already a challenge like this one?
• Is there any blatant loophole/possible imporvements?
• What tag(s) do you recommend for this challenge? (please edit the answer)

Answer 27

Every Nth Line in Source Outputs N

code-challenge source-layout

Heavily inspired by Hello, World! (Every other character)

Related to my other Sandbox post Every Nth Char in Source Outputs N; is it a dupe?

Write a program that outputs 1. When the first, third, fifth, etc. lines are removed, it outputs 2. When all lines where their (1-based) index in the source, mod N, are not 0, are removed, it should output N.

This is code-challenge. The winner is the program that works with the largest N, while working for all n < N (obviously, to run up to N, it has to be at least N lines long). If there is a tie, the winner is the shortest answer that reaches the largest N. Your program must at least work up to N=2, since I don't think any languages will struggle with simply printing 1.

Example

Examples are based off of this sample program:

test
hi
world
hello
12345
System.out.println(test);
timeout
let's dance

For the program to work for N=1, the original program should output 1.

For the program to work for N=2, the following should output 2:

hi
hello
System.out.println(test);
let's dance

For the program to work for N=3, the following should output 3:

world
System.out.println(test);

For the program to work for N=4, the following should output 4:

hello
let's dance

For the program to work for N=5, the following should output 5:

12345

etc.

The highest N this program could work for is its line length, 8.

Answer 28

Sandboxing this mostly so I don't forget about it (as I don't want to initiate this so soon after v3). Unlikely to need any serious revision, but comments are appreciated none the less.

Prisoner's Dilemma v4: The Amnesiac Gentlemen.

This is similar to v3 Petri Dilemma, except with one significant change: no one knows what round it is. The same setup, submission format, and scoring will be used. For sandbox brevity, I'm only noting the differences from v3.

Bots will receive input at the beginning of its turn in the format:

current points, enemies points, your previous moves, enemy's previous moves

The format of the move list (both yours and the enemy's) will be a string of characters, "c" for cooperation "d" for defection, in order from first round to last. However this list will contain only the first seven moves of the game as well as the most recent 7 moves (as everyone knows, you can only hold seven items in working memory). A String 14 characters or fewer would indicate a round at the beginning of the game where 14 total moves haven't yet been performed. Later rounds would be indeterminate.

Additionally, as the current round number is not being passed in, bots will be unaware of when the end of the game comes (games will still be 200 rounds). This should prevent "Ah ha, last round, I backstab!" "Ah ha, but I backstab you first, one round earlier!" strategies, which is what dominated a large swath of the v3 strategic playspace (I did tests where all backstab-early bots were coded to all backstab on the same round and there were only two that performed sub-optimally as a result, both of which were set to backstab "before all n-Tit-for-Tat strategies", moving them back 1 rounds re-elevated them above n-Tit-for-Tat again, as well as which one backstabbed the other first determining the winner between them). While several bots from v3 would be valid submissions in v4, all of the winning bots utilize more data than v4 will let them have, opening up the playing field for new techniques.

Here are four sample strategies that will be entered to start with:

Tit for Tat

def titfortatfunc(mypoints, enpoints, mylist, enlist):
    if not enlist or enlist[counter-1] == "c":
        return "c"
    else:
        return "d"

RandomPick

from random import choice
def randompickfunc(mypoints, enpoints, mylist, enlist):
    return choice(["d", "c"])

Cooperator

def cooperatorfunc(mypoints, enpoints, mylist, enlist):
    return "c"

Defector

def defectorfunc(mypoints, enpoints, mylist, enlist):
    return "d"

Answer 29

(Code Golf) How Many Notes Are There?

Background

Most music games (MUG) describes the "instructions" that the player must follow as "notes". When the charts (set of notes) are first available, MUG players usually record the chart as a video and upload them to video sites. However, unless playing a full combo (able to pick up all notes) that the combo count directly shows the number of notes, it is usually not practical to count the number of notes one by one directly (since there are usually hundreds of notes), so they calculate that from the scores that may show on those videos if the score formula is known.

One of those examples is jubeat, which is somehow like a MUG version of "Whack-a-Mole". Although officially "instructions" are called "chips", players have the consensus to call them "notes". (For those who don't know what jubeat is please check it out here: jubeat - RemyWiki)

Objective

What you have to do, is to:

• Write a program or function,
• Which accepts a list of integers as the only input,
• That calculates the numbers of notes which is possible for all the given "basic scores".

Requirements

• The input can be an array of integers or a string containing those integers (Please indicate the input format).
• The integers in the input are guaranteed to be in the range of [0, 900000] inclusive.
• A case (NOTES in the formula) is possible means that, for each integer in the input, there exists a variable ACH, when substituted into the formula below, the formula evaluates to that integer. (See The Formula and Test Cases for details)
• All possible cases within the range [1, 1100] inclusive must be included in the output.
• The output can be an array of integers or a string containing the results (Please indicate the output format).
• If there is no case fulfilling the requirements, the program or function should either return an empty array, an empty string, null, or any objects indicating absence of results.
• NO RUNTIME EXCEPTIONS shall be thrown in any circumstances.

The Formula

The max score is 1000000, but here we only consider BASIC_SCORE, whose maximum is 900000.

The BASIC_SCORE is calculated by BASIC_SCORE = floor(floor(ACH * 100000 / NOTES) * 0.9), where ACH is an integer in the range [0, NOTES*10] inclusive except NOTES*10-1 and NOTES*10-2.

As a concrete example, take ACH=6850, NOTES=900, we have BASIC_SCORE = floor(floor(6850 * 100000 / 900) * 0.9) = 684999.

As a result, NOTES=900 is a possible case for the basic score 684999.

Test cases

 Input                                    | Output
-----------------------------------------------------------------------------------------
 896757, 846353, 844486                   | 916
 891000, 893999                           | (all multiples of 30 within [1, 1100])
 899736                                   | 1024, 1025, 1026, 1027
                                          | (342, 683, 684 are false positives because  
                                          |  in these cases ACH = NOTES*10-1 or 
                                          |  ACH = NOTES*10-2)
 873540, 802468                           | (none: no case fits all inputs.
                                          |  some cases do fit some inputs but not all)
 0, 900000                                | (all values within [1..1100])
 800000                                   | (none)

Rules and Winning Criteria

This is a code-golf, so the source code with the shortest length (in terms of bytes) wins. Standard loopholes apply.

Answer 30

Poor Man's Ransomware

This challenge is loosely inspired by the cheapo-enigma machine question. However, I beleive that the differences are substantial enough that this would not be a dupe. Feedback welcome.

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You have been captured by a morally questionable "employer" and forced to write a piece of "ransomware". All it has to do is take in a string "in whatever format" and output another string (which can be used to recover the files) Essentially, across the set of all possible inputs (infinite) you will define a one to one function.

Participants will then publish their code to stack-exchange, where other aspiring "hackers" will try to break your code. A "cop" submission will consist of a byte count a sample plaintext and a sample "encrypted" file as well as an encrypted copy of your code.

Robbers will work tirelessly in another thread to reproduce your code. Any submission which correctly produces the corresponding "encrypted" files when fed the sample plaintext and itself will be considered to be cracked.

If your code lasts 7 days or longer you may mark your submission as "safe" by publishing the source code for the encryptor and a decryptor. Until this time robbers may still work to break your code. If anyone finds that a specific decryptor fails on a certain plaintext it is invalid.

The winning cop has the shortest safe submission and the winning robber has the largest sum of the bytes of his cracked cops. Ties go to the earlier poster. Good Luck!