# 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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### Do you win a Numeric Mahjong?

Background Numeric Mahjong is a hypothetical variation of Japanese Mahjong, played with nonnegative integers instead of Mahjong tiles. Given a list of nonnegative integers, it is a winning hand if it ...
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2k views

### 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 ...
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382 views

### 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 ...
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2k views

### 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 ...
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2k views

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 \\$...
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3k views

### 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, <...
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939 views

### 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, ...
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### 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 ...
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