Indeed this is precisely Algorithm L of section 7.2.1.2 “Generating all permutations” (described on its very first page [1]), and is also what is used by C++'s

Indeed this is precisely Algorithm L of section 7.2.1.2 “Generating all permutations” (described on its very first page [1]), and is also what is used by C++'s `next_permutation`, among others. There are a few expositions of it online [2] (including this 2008 StackOverflow answer of mine: [3]). [1] Draft version of Knuth's Fascicle 2B: http://www.cs.utsa.edu/~wagner/knuth/fasc2b.pdf#page=5 http://www.cs.utsa.edu/~wagner/knuth/fasc2b.pdf#page=5 (now page 319 of Volume 4A) [2]: https://www.quora.com/How-would-you-explain-an-algorithm-that-generates-permutations-using-lexicographic-ordering https://www.quora.com/How-would-you-explain-an-algorithm-tha... [3]: https://stackoverflow.com/a/353248/4958 https://stackoverflow.com/a/353248/4958