Sleep Sort

Published on 07 October 2019 (Updated: 05 July 2025)

Welcome to the Sleep Sort page! Here, you'll find a description of the project as well as a list of sample programs written in various languages.

This article was written by:

Jeremy Grifski
rzuckerm

Description

Sleep sort is a sorting algorithm that for each input numeric variable it starts a thread (or thread like process) that automatically goes to sleep for given number of time units, eg. seconds. When a thread complets, it returns the number. When all threads complete, a sorted array of numbers is returned.

Performance

Time complexity of this algorithm strictly depends on value of the highest number, therefore it's always O(n), space complexity is dependent on numbers of threads started - O(n) where n is number of inputs.

Requirements

Write a sample program that takes a list of numbers in the format "4, 5, 3, 1, 2". It should then sort the numbers and output them:

$ ./sleep-sort.lang "4, 5, 3, 1, 2"
1, 2, 3, 4, 5

Testing

Every project in the Sample Programs repo should be tested. In this section, we specify the set of tests specific to Sleep Sort. In order to keep things simple, we split up the testing as follows:

Sleep Sort Valid Tests
Sleep Sort Invalid Tests

Sleep Sort Valid Tests

Description	Input	Output
Sample Input	"4, 5, 3, 1, 2"	"1, 2, 3, 4, 5"
Sample Input: With Duplicate	"4, 5, 3, 1, 4, 2"	"1, 2, 3, 4, 4, 5"
Sample Input: Already Sorted	"1, 2, 3, 4, 5"	"1, 2, 3, 4, 5"
Sample Input: Reverse Sorted	"9, 8, 7, 6, 5, 4, 3, 2, 1"	"1, 2, 3, 4, 5, 6, 7, 8, 9"

Sleep Sort Invalid Tests

Description	Input
No Input
Empty Input	""
Invalid Input: Not A List	"1"
Invalid Input: Wrong Format	"4 5 3"

All of these tests should output the following:

Usage: please provide a list of at least two integers to sort in the format "1, 2, 3, 4, 5"

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