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Questions tagged [decision-problem]

For challenges which involve deciding whether or not the input meets certain criteria, and outputting some data, representing that decision.

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236 votes
369 answers

Is this number a prime?

Believe it or not, we do not yet have a code golf challenge for a simple primality test. While it may not be the most interesting challenge, particularly for "usual" languages, it can be nontrivial in ...
Dennis's user avatar
  • 210k
71 votes
48 answers

Write the shortest self-identifying program (a quine variant)

Write a program that will generate a "true" output iff the input matches the source code of the program, and which generates a "false" output iff the input does not match the source code of the ...
PhiNotPi's user avatar
  • 29.1k
94 votes
163 answers

Determine whether strings are anagrams

Challenge Given two strings, work out if they both have exactly the same characters in them. Example Input word, wrdo This returns true because they are the ...
Tom Gullen's user avatar
  • 1,249
79 votes
261 answers

Is this even or odd?

Note: There is not been a vanilla parity test challenge yet (There is a C/C++ one but that disallows the ability to use languages other than C/C++, and other non-vanilla ones are mostly closed too), ...
Matthew Roh's user avatar
  • 5,347
62 votes
48 answers

Are the brackets fully matched?

You must write a program or function that takes a string of brackets and outputs whether or not that string is fully matched. Your program should print a truthy or falsy value, and IO can be in any ...
DJMcMayhem's user avatar
  • 59.3k
47 votes
79 answers

Is it a leap year?

This challenge is quite simple. You will take an input which will be a year from 1801 to 2400, and output if it is a leap year or not. Your input will have no newlines or trailing spaces: ...
user avatar
52 votes
81 answers

It's Hip to be Square

Challenge So, um, it seems that, while we have plenty of challenges that work with square numbers or numbers of other shapes, we don't have one that simply asks: Given an integer ...
Shaggy's user avatar
  • 42.2k
41 votes
9 answers

"Convenient palindrome" checker

If you've ever tried to write palindromic code before, you'd know how much brackets tend to get in your way. ()() is not a palindrome, even though it kinda looks ...
algorithmshark's user avatar
29 votes
69 answers

Is string X a subsequence of string Y?

Given strings X and Y, determine whether X is a subsequence of Y. The empty string is regarded as a subsequence of every string. (E.g., '' and ...
r.e.s.'s user avatar
  • 3,132
16 votes
2 answers

Golf the prime numbers in Shue

I'd like to introduce a new? programming language I call Shue (Simplified Thue). It has very simple syntax. Here is a program that checks if an input is divisible by three: ...
AnttiP's user avatar
  • 7,898
74 votes
52 answers

Check if words are isomorphs

Two words are isomorphs if they have the same pattern of letter repetitions. For example, both ESTATE and DUELED have pattern <...
xnor's user avatar
  • 145k
58 votes
70 answers

Am I a Fibonacci Number?

Your Task: Write a program or function to check if a number that is inputted is a Fibonacci number. A Fibonacci number is a number contained in the Fibonacci sequence. The Fibonacci Sequence is ...
Gryphon's user avatar
  • 7,235
29 votes
13 answers

Word Search Puzzle

Given a rectangular text as a word search puzzle and a search string, determine if the text contains the search string. The search string may appear: horizontally, vertically or diagonally forwards ...
Martin Ender's user avatar
12 votes
19 answers

Find a Rocco number

I was asked this question in an interview but I was unable to figure out any solution. I don't know whether the question was right or not. I tried a lot but couldn't reach any solution. Honestly ...
vijayscode's user avatar
57 votes
79 answers

Test a number for narcissism

A Narcissistic Number is a number which is the sum of its own digits, each raised to the power of the number of digits. For example, take \$153\$ (3 digits): \$1^3 + 5^3 + 3^3 = 153\$ \$1634\$: \$1^...
Iszi's user avatar
  • 2,537
37 votes
43 answers

Numbers with Rotational Symmetry

Given an integer, output a truthy value if it is the same upside-down (rotated 180°) or a falsy value otherwise. 0, 1, and ...
mbomb007's user avatar
  • 23.4k
35 votes
50 answers

Will Jimmy fall off his platform?

Backstory Meet my friend Jimmy: /o\ Jimmy is a little character who likes to stand on platforms. Here's Jimmy safely standing on a platform: ...
moltarze's user avatar
  • 2,570
55 votes
102 answers

Is it double speak?

In an earlier challenge I asked code golfers to produce strings which copy each character in a string. For example: TThhiiss iiss ddoouubbllee ssppeeaakk!! This ...
AJFaraday's user avatar
  • 11.8k
99 votes
36 answers

Would this string work as string?

Write a program that takes a single line string that you can assume will only contain the characters /\_‾. (That's forward and backward slash, underline and ...
Discrete Games's user avatar
81 votes
94 answers

Golf all the 16 logic gates with 2 inputs and 1 output!

For example, the gate A and B is a logic gate with 2 inputs and 1 output. There are exactly 16 of them, because: each logic gate takes two inputs, which can be ...
Leaky Nun's user avatar
  • 49.9k
49 votes
71 answers

An abundance of integers!

An Abundant number is any number where the sum of its proper divisors is greater than the original number. For example, the proper divisors of 12 are: ...
DJMcMayhem's user avatar
  • 59.3k
37 votes
36 answers

Manage Trash So

It's become somewhat of a tradition in PPCG that some users temporarily change their names by an anagram (a new name formed by reordering the letters of the old). Sometimes it gets difficult to find ...
Luis Mendo's user avatar
  • 105k
31 votes
30 answers

Is it a Bumpy Word?

(inspired by this challenge over on Puzzling -- SPOILERS for that puzzle are below, so stop reading here if you want to solve that puzzle on your own!) If a letter in a word occurs alphabetically ...
AdmBorkBork's user avatar
  • 43.5k
27 votes
2 answers

Arranging arbitrary rectangles to fill a space

Can these rectangles fill a rectangular space? Given a bunch of rectangles, you are asked whether or not they can be arranged to fill a rectangular space. Specs Given a bunch of arbitrary ...
hyper-neutrino's user avatar
  • 42.5k
21 votes
18 answers

Check if all non-zero elements in a matrix are connected

Input: A matrix containing integers in the range [0 - 9]. Challenge: Determine if all non-zero elements are connected to each other vertically and/or horizontally. Output: A truthy value if all ...
Stewie Griffin's user avatar
380 votes
1 answer

Regex that only matches itself

There are some pretty cool challenges out there involving regex (Self-matching regex, Regex validating regex) This may well be impossible, but is there a regex that will ONLY match itself? NOTE, ...
Dylan Madisetti's user avatar
66 votes
11 answers

Only Even Bytes

The scenario Lately you have been noticing some strange behavior with your favorite text editor. At first it seemed that it was ignoring random characters in your code when writing to disk. After a ...
Wheat Wizard's user avatar
  • 99k
57 votes
136 answers

Is this number evil?

Introduction In number theory, a number is considered evil if there are an even number of 1's in its binary representation. In today's challenge, you will be identifying whether or not a given number ...
Amphibological's user avatar
53 votes
100 answers

Is it a pangram?

Write a function or program that takes as its input a string and prints a truthy value if the string is a pangram (a sequence of letters containing at least one of each letter in the English alphabet) ...
Arcturus's user avatar
  • 7,387
50 votes
92 answers

Is this number a factorial?

The Task Given a natural number as input, your task is to output a truthy or falsey value based on whether the input is a factorial of any natural number. You can assume that the input number will ...
Arjun's user avatar
  • 5,074
46 votes
34 answers

Wait, what language is this?

Recently I had the pleasure of writing a Haskell program that could detect if the NegativeLiterals extension was engaged. I came up with the following: ...
Wheat Wizard's user avatar
  • 99k
46 votes
19 answers

Lever Simulator 2015

Why a Simulator? Kids these days don't have the time nor the ambition to actually go and stack boxes on the see-saw or play around with balancing physical objects. This leaves lots of room in the ...
turbulencetoo's user avatar
45 votes
77 answers

Is this number triangular?

Challenge Given a positive integer, determine whether it is a triangular number, and accordingly output one of any two constant, distinct values. Definition A triangular number is a number that can be ...
ETHproductions's user avatar
38 votes
3 answers

Primality testing formula

Your goal is to determine whether a given number n is prime in the fewest bytes. But, your code must be a single Python 2 expression on numbers consisting of only ...
xnor's user avatar
  • 145k
35 votes
40 answers

Is it almost-prime?

Sandbox Definition: A positive integer n is almost-prime, if it can be written in the form n=p^k where ...
infinitezero's user avatar
  • 1,646
34 votes
44 answers

Is it a Lynch-Bell number?

You will be given a positive, whole number (that will never contain a 0) as input. Your task is to check whether it is a Lynch-Bell number or not. A number is a Lynch-Bell number if all of its digits ...
Okx's user avatar
  • 16.4k
33 votes
27 answers

Stackable sequences

You deal cards labeled 0 to 9 from a deck one a time, forming stacks that start at 0 and count up by 1. When you deal a 0, you place it on the table to start a new stack. When you deal any other ...
xnor's user avatar
  • 145k
29 votes
4 answers

Golf Me An OOP!

Golf Me An OOP! Two important components of object-oriented programming are inheritance and composition. Together, they allow for creating simple yet powerful class hierarchies to solve problems. ...
user avatar
26 votes
28 answers

Can Jimmy hang on his rope?

Yet another Jimmy challenge by his original father. See these other lovely challenges. As you all know, recently we've been seeing challenges related to Jimmy on platforms. Now, Jimmy is an acrobat ...
moltarze's user avatar
  • 2,570
24 votes
22 answers

Create a sudoku solution CHECKER

Create a Sudoku solution CHECKER There are oodles of Sudoku SOLVERS here, but I want you to create a solution CHECKER as small as humanly possible (code-golf). A valid entry will be able to either ...
David Wilkins's user avatar
22 votes
4 answers

Is it a valid chess move?

Alternate name: ChessMoveQ Given a list of up to 32 elements, each consisting of 4 elements, and a second list with 4 elements, determine whether the move detailed ...
caird coinheringaahin g's user avatar
22 votes
10 answers

Can the maze be solved?

Task Print 0 if an n*m maze cannot be solved Print 1 if an n*m maze can be solved (in 1 or more ways) (so I'm not asking for ...
dwana's user avatar
  • 551
19 votes
10 answers

Bracket balancing

You will be given a (possibly empty) string containing brackets ([{()}]) and any other characters (A-...
ghosts_in_the_code's user avatar
17 votes
14 answers

We do tower hopping

Task Given an array of non-negative integers a, determine the minimum number of rightward jumps required to jump "outside" the array, starting at position ...
0x45's user avatar
  • 800
15 votes
9 answers

Parity of a Permutation

Background The parity of a permutation, as defined by wikipedia, is as follows: The sign or signature of a permutation σ is denoted sgn(σ) and defined as +1 if σ is even and −1 if σ is odd. The sign ...
Patrick Roberts's user avatar
14 votes
22 answers

Determine if an integer is a palindrome in a given radix (base)

Write a program that reads from stdin two integers, each newline terminated, hereafter called "number" and "radix", and: Prints any fixed message you want if the number is a palindrome in that radix (...
durron597's user avatar
  • 4,810
118 votes
76 answers

I'm a palindrome. Are you?

There have been a couple of previous attempts to ask this question, but neither conforms to modern standards on this site. Per discussion on Meta, I'm reposting it in a way that allows for fair ...
user avatar
90 votes
108 answers

Count of "a"s and "b"s must be equal. Did you get it computer?

In the popular (and essential) computer science book, An Introduction to Formal Languages and Automata by Peter Linz, the following formal language is frequently stated: $$\large{L=\{a^n b^n:n\in\...
user avatar
84 votes
42 answers

Non-discriminating Programming

We say a string is non-discriminating if each of the string's characters appears the same number of times and at least twice. Examples "aa!1 1 !a !1" is non-...
Laikoni's user avatar
  • 26.2k
55 votes
63 answers

Is this string a square?

A string is considered to be square if the following conditions are met: Each line has the same number of characters The number of characters on each line is equal to the number of lines. Your task ...
Pavel's user avatar
  • 9,377

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