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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23 votes
23 answers
3k views

Is it a row of Pascal's triangle?

Pascal's triangle is a triangular diagram where the values of two numbers added together produce the one below them. This is the start of it: ...
  • 33.6k
11 votes
5 answers
442 views

Parse Ternary Lambda Calculus for correctness

Wheat Wizard has once tried to come up with a parsing problem unsuitable for regex, but it failed due to Anders Kaseorg's Perl regex answer. This is the second attempt. Now that we know that Perl ...
  • 69.3k
25 votes
5 answers
1k views

Parse a lambda for correctness

The goal of this challenge is to fill a niche that is mostly lacking on this site. In my observations there most parsing verification challenges fall into two categories: Super easy parsing. This ...
  • 92.2k
13 votes
2 answers
511 views

Is this an interval graph?

Background An interval graph (Wikipedia, MathWorld, GraphClasses) is an undirected graph derived from a set of intervals on a line. Each vertex represents an interval, and an edge is present between ...
  • 69.3k
8 votes
5 answers
341 views

Will Alice win in this Stick Bomber game?

Background Stick Bomber is a two-player game I just made up. Initially, some sticks are placed in one or more groups, and the sticks in each group are laid out in a straight line. So a configuration ...
  • 69.3k
16 votes
19 answers
1k views

Compare positions of integers in this sequence

A001057 is one way to represent an integer as a natural number. It lists them according to the following pattern: 0, 1, -1, 2, -2, 3, -3, 4, -4, ... In this ...
18 votes
3 answers
733 views

Sliding Dice in a Dish

We have 3 dice in a square dish. The dish is 8 units wide and tall and each die is 3 units wide and tall. The dice are facing up each with a different number on their top face. ...
  • 92.2k
21 votes
11 answers
2k views

Is this a Jordan matrix?

Background A Jordan matrix is a block-diagonal matrix where each block on the diagonal has the structure of $$ \begin{bmatrix} \lambda & 1 & 0 & \cdots & 0 \\ 0 &...
  • 69.3k
5 votes
3 answers
160 views

Is this an ordinal transform? [duplicate]

Related: What's my telephone number? which asks to calculate the terms of A000085, the number of possible ordinal transforms of length n. Background Ordinal transform is a transformation on an integer ...
  • 69.3k
30 votes
14 answers
2k views

Is it a Giuga number?

Giuga numbers (A007850) are composite numbers \$n\$ such that, for each prime factor \$p_i\$ of \$n\$, \$p_i \mid \left( \frac n {p_i} -1 \right)\$. That is, that for each prime factor \$p_i\$, you ...
20 votes
6 answers
2k views

Recognize most smaller primes with a regex

This time, you are working on a regex. Your regex is meant to approximately full-match the base-10 representations of primes \$0 \le p < 1000\$, while ignoring any non-numeric string or composite ...
32 votes
46 answers
3k views

Is this a Permutation of 1..n

Input a non-empty array with \$n\$ positive integers. Test if the input array contains every integer in \$1\cdots n\$. In case you prefer 0-indexed numbers, you may choose to input an array of non-...
  • 32.1k
30 votes
12 answers
2k views

Is it a checkered tiling?

Background A checkered tiling of a rectangular grid is a tiling using some polyominoes, where each region can be colored either black or white so that no two polyominoes sharing an edge has the same ...
  • 69.3k
34 votes
26 answers
4k views

Is there a single straight line in the matrix?

Inspired by Wzl Determine if a given square binary matrix has exactly one row or column consisting of entirely 1s, and the rest of the matrix is ...
20 votes
16 answers
2k views

Is there a left-right connection?

Task Given a square array of 0s and 1s, determine whether or not there exists a path of 1s connecting the leftmost and rightmost columns. A path can take steps of one unit up, down, left or right, ...
  • 541
26 votes
9 answers
2k views

Is it a valid Parker Square

5 Years ago, this happened, and then it became sort of a meme. Challenge The Challenge today is, to check if a "magic square" is a valid parker square. What is a Real Magic square? All the ...
  • 6,366
17 votes
7 answers
2k views

But, Is It Art?

But Is It Art? is an esolang created by ais523, where one step is break the program into orthogonally connected "tiles": A BBBB A B B AA CC A CC Each ...
22 votes
1 answer
727 views

Help me prove the Four Color Theorem!

This is not just another challenge asking you to color random maps... In this challenge, you are asked to write a program that is actually used in the formal proof of the Four Color Theorem. First I ...
  • 749
13 votes
8 answers
1k views

Is this FEN board a Fischer random chess starting board?

Introduction Fischer random chess, also known as Chess960 for the 960 valid starting boards, is a variant of chess where each player's pieces are randomly shuffled at the start. As a reminder, each ...
  • 11.3k
32 votes
86 answers
7k views

iHateOddNumbers

Task Given a non-negative number, check if it's odd or even. In case it's even, output that number. Otherwise, throw any exception/error that your language supports, and stop the program. Example with ...
16 votes
2 answers
315 views

Solve the halting problem for S combinatory logic

Background Combinatory logic is a system where a term is written using a finite set of combinators and function application between terms, and reduction rules are defined for each combinator. The well-...
  • 69.3k
3 votes
8 answers
911 views

Are vertices in a clockwise order?

Your program must accept as input six numbers, which describe a triangle - for example, the inputs 80, 23, 45, 1, 76, -2 describe a triangle with vertices (80, 23), (45, 1), and (76, -2). The input ...
25 votes
14 answers
1k views

1D monochrome Link-a-Pix solvability

Background Link-a-Pix is a puzzle on a rectangular grid, where the objective is to reveal the hidden pixel art by the following rules: Connect two cells with number N with a line spanning N cells, so ...
  • 69.3k
18 votes
9 answers
1k views

Dimensional Chess positions

Task Any one of these two: Determine if a given position (an ordered non-empty collection of integers in the range ‒8 to 8, or ‒7 to 7 if you want) is a valid Dimensional Chess position. List all the ...
  • 29.1k
24 votes
4 answers
2k views

Is it a chess cycle?

Inspired by a discussion from the Esolangs.org unofficial Discord Server. Instructions A chess cycle is an arrangement of a chess board where each piece must attack one other piece, and only one other ...
  • 26.6k
9 votes
1 answer
174 views

Are We Fast And Furious? [closed]

There are currently nine feature length films in the core Fast & Furious/The Fast and the Furious media franchise, a series of films about bald men scowling and driving cars very fast. The names ...
13 votes
2 answers
297 views

Determine if a dot(comma) program halts

Dotcomma is a simple esolang I made a while ago that only uses four operators: [.,]. In this challenge, you'll determine if a dotcomma program consisting only of <...
26 votes
5 answers
2k views

I before E, except after C

You may be aware of the famous old rhyme, "I before E, except after C". It is a rule taught to aid in the spelling of certain English words. Quoting Wikipedia: If one is not sure whether a ...
  • 20.3k
25 votes
57 answers
2k views

Are All the Items the Same?

Given a list of non-negative integers, return whether or not that list is all the same number. Rules Input and output can be taken/given in any reasonable and convenient format Truthy/Falsey values ...
  • 26.3k
18 votes
19 answers
3k views

Did I die or not?

Given a permutation of the alphabet and an intended "word", determine if the word was guessed in a game of Hangman, where the permutation is the list of guesses. For example, given ...
10 votes
6 answers
382 views

Rejecting invalid IPv4 addresses

I want to avoid responding to illegal or spoofed addresses. One type that's easy to detect is an address that should not exist on a packet received by my router: a special-use address. Challenge Given ...
  • 201
17 votes
19 answers
1k views

Check B-powersmoothness

from Wikipedia, a number is called B-powersmooth if all prime powers \$p^v\$ that divide the number satisfy \$p^v \leq B\$. B-powersmoothness is important, for example, for Pollard's p-1 factorization ...
12 votes
15 answers
794 views

Check if B is composed of substrings of A of length n

Given two strings \$ A \$ and \$ B \$ and a positive integer \$ n \$, determine whether \$ B \$ is composed entirely of (possibly overlapping) strict substrings of \$ A \$ of a length of at least \$ ...
  • 23k
23 votes
5 answers
1k views

Can this pattern be made with dominoes?

Given a pattern of squares on a grid, determine if it is possible to create that pattern with non-overlapping dominoes. In case you are not familiar, a domino is a rectangular shape created by joining ...
  • 9,841
25 votes
10 answers
1k views

Unique half rainbows

If we take a positive integer \$n\$ and write out its factors. Someone can determine \$n\$ just from this list alone. In fact it is trivial to do this since the number is its own largest factor. ...
  • 92.2k
13 votes
4 answers
1k views

I ain't no Fortunate sum

The primorial \$p_n\#\$ is the product of the first \$n\$ primes. The sequence begins \$2, 6, 30, 210, 2310\$. A Fortunate number, \$F_n\$, is the smallest integer \$m > 1\$ such that \$p_n\# + m\$ ...
27 votes
11 answers
2k views

Test if a Gray code is Beckett

Background An \$n\$-bit Gray code is an ordering of \$2^n\$ binary sequences so that adjacent sequences always differ by exactly one bit. A Beckett-Gray code is a special kind of Gray code. In ...
  • 69.3k
20 votes
1 answer
410 views

Is this Game of Go configuration fully alive?

Background This challenge is about the Game of Go. Here are some rules and terminology relevant to this challenge: Game of Go is a two-player game, played over a square board of size 19x19. One of ...
  • 69.3k
25 votes
13 answers
5k views

Is it a vampire number?

Repost and improvement of this challenge from 2011 A vampire number is a positive integer \$v\$ with an even number of digits that can be split into 2 smaller integers \$x, y\$ consisting of the ...
15 votes
6 answers
820 views

Golf this Thumb-2 Constant!

One thing that is constantly frustrating when golfing ARM Thumb-2 code is generating constants. Since Thumb only has 16-bit and 32-bit instructions, it is impossible to encode every immediate 32-bit ...
  • 4,500
25 votes
14 answers
4k views

Is this an L-shape?

Background An L-shape is defined as a polyomino which can be made by extending two rectangular legs in orthogonal directions from a full square (called a pivot). The size of the square should be at ...
  • 69.3k
32 votes
16 answers
6k views

Is it a lobster number?

Introduction A "lobster number", by my own designation, is a number that contains within itself all of its prime factors. The "lobster" description was inspired by the recent ...
  • 429
12 votes
3 answers
420 views

A graph and its seven closures

Background A little while ago, someone posted an interesting puzzle on Math.SE: What is the smallest digraph (directed graph) G where the following eight graphs are all distinct: G, the original ...
  • 69.3k
14 votes
8 answers
2k views

Is my triangle on the lattice?

Write a program or function which takes three positive integers \$a, b, c\$ and returns/outputs one value if there is, and a different value if there isn't, a triangle on the square lattice, whose ...
  • 407
9 votes
3 answers
958 views

Validating a Battleship board

Do you know the game Battleship? Well, I want to play with my little brother, but before we can begin we need to set up our ships on the board. This is your input. Now, we need to check that the ships ...
20 votes
19 answers
2k views

Vandalizing Marquees

A marquee is a low-tech board that allows customizable letters. For example, here is a marquee: SALE ON SNEAKERS However, someone might come along and vandalize it ...
  • 13.6k
9 votes
8 answers
513 views

Equality up to Swapping

inputs / outputs your program/function/routine/... will be a predicate on two tuple sequences; call it relation . for the purpose of simplicity we use natural ...
  • 59
13 votes
2 answers
411 views

Can you make your way through the Ulam spiral?

You will be given a point (x,y) relative to the center of the Ulam spiral (the center being the point which represents one), and length ...
30 votes
21 answers
3k views

Can we spell a third number?

You are given two strings, each consisting of the English word for a number between 1 and 13: ...
  • 176k
21 votes
23 answers
1k views

Compatible strings

When studying numerology, you can say two words (strings consisting entirely of letters) are compatible if they produce the same number under the following operation (let's use the string ...

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