Questions tagged [self-validating]

A restricted-source challenge where the task is to check the source restriction. This means when fed itself as input the program must output true.

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77 votes
38 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-...
  • 25.5k
40 votes
12 answers

A well linked challenge

An activity I sometimes do when I'm bored is to write a couple of characters in matching pairs. I then draw lines (over the tops never below) to connect these characters. For example I might write \$...
  • 94.1k
23 votes
16 answers

A Semi-palindrome Puzzle

An palindrome is a word that is its own reverse. Now there are some words that might look like palindromes but are not. For example consider the word sheesh, <...
  • 94.1k
20 votes
17 answers

Appearing a unique number of times

Your task is to write a program or function that takes as input a list of positive integers and determines if there are any two integers in the list, that both appear the same number of times. For ...
  • 94.1k
19 votes
12 answers

In for a bumpy ride

Your task is to write a computer program or function that takes a list of nonnegative integers of at least length 2 and determines if they are a "zigzag". A sequence is a zigzag if and only ...
  • 94.1k
17 votes
9 answers

Exactly two neighbors

Given as input a list of positive integers, your task is to determine if every integer present has exactly two neighbors in the list. The neighbors of a integer \$x\$ are the distinct integers that ...
  • 94.1k
11 votes
3 answers

Unique rainbow programs

Given a list of positive integers as input you are to determine if there is a way to pair up the elements such that: All but one element is in a pair No element is in more than one pair Every pair is ...
  • 94.1k
6 votes
6 answers

Lucas and Fibonacci are in pair

Influenced by Non-discriminating Programming, I made up an idea of a similar challenge. Here, we say a string is a Lucas string if the number of appearances of each character is a Lucas number (2, 1, ...