Questions tagged [decision-problem]
For challenges which involve deciding whether or not the input meets certain criteria, and outputting some data, representing that decision.
799 questions
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Identify Redundant Regex
A redundant regular expression (regex) is defined here as a regex which has some amount of characters which can be removed while not affecting its functionality -- i.e. it matches the exact same set ...
- 7,465
10
votes
2
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379
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Check if a number is a power with its program value being a power
Task:
Your task is make a program to check if there exists integers \$a \ge 2, b \ge 2\$ such that \$a^b=i\$ where \$i\$ is the input integer at least 2.
The catch is that your program must return a ...
- 5,105
15
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17
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IMO 2025: Divisor sums that go forever
Problem 4 of the 2025 International Mathematical Olympiad asked (paraphrased):
Let \$f(n)\$ be the sum of the largest three proper divisors of \$n\$,
that is divisors excluding \$n\$ itself. For ...
- 150k
23
votes
15
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Write two very different programs with the same characters
Your task is to write two programs/functions, in the same language.
Program 1: Verify that two inputs are anagrams of each other.
Program 2: Verify that two inputs differ from each other at every ...
- 8,074
12
votes
3
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The shortest NP-complete problem
Find an NP-complete problem that covers all finite ASCII strings, and present a solver for the problem in the programming language of your choice.
By the definition, if there is a finite ASCII string ...
- 7,381
28
votes
42
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Does your source code contain this character?
Given a character as input, determine if your source code contains that character or not.
Shortest code wins. Though, I'd like to see some "normal" languages too.
UPDATE: the question ...
- 333
8
votes
12
answers
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The Array Walker (part 2)
The Array Walker (part 2)
Input: A non-empty array of integers (without nesting1). This can have negative values!
Output: A boolean value2 indicating whether we can reach the end of the array when ...
- 391
8
votes
23
answers
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Can we escape from array?
Can we escape from the array?
Input: A non-empty array of non-negative integers (without nesting1).
Output: A boolean value2 indicating whether we can reach the end of the array when starting from the ...
- 391
10
votes
2
answers
706
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Intersection check in the fewest operations
Challenge
Given two line segments, your goal is to write a function which determines if they intersect using only the operations given below:
Multiplication: x*y
...
- 5,566
3
votes
2
answers
220
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Winding a Queue
You will be given a matrix. It contains a ride exit (with a direction), some path, as well as some obstacles. Your goal is to build the longest possible queue line in that space, which connects the ...
- 2,407
13
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7
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Traverse the list
Update 2025-06-04: Thanks for the submissions everyone! It seems like a lot of the solutions are quite slow / timeout for the 100 length test case, so I don't think any will be able to do the 10k. ...
- 2,407
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votes
12
answers
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A broken clock is right n times a day
You will be provided with a string containing a digital clock. You must determine how many times per day that clock could be correct. You can ignore daylight savings time. You do not know if the clock ...
- 2,407
7
votes
4
answers
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Ray's intersecting lines
Ray has created some ASCII lines which he is using to draw with on a canvas.
His canvas can be any width and height between 1 to 100 characters (the borders do not count towards these dimensions). He ...
- 2,407
13
votes
18
answers
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Is it a product of 4 unique primes (A046386)?
A046386 is the sequence of all natural numbers that are the product of exactly 4 distinct primes.
Write the shortest program, function, or code snippet, that, when given a natural number, outputs ...
- 11.5k
9
votes
2
answers
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Primitive words
Given a list of values, 1, 2, -1, or -2, we will allow the following simple moves:
Remove adjacent values which are negatives of each other. e.g. ...
- 103k
