We just generate them on the fly - after all we're not stupid ;-) https://en.wikipedia.org/wiki/Permutation#Algorithms_to_generate_permutations https://en.wiki

We just generate them on the fly - after all we're not stupid ;-) https://en.wikipedia.org/wiki/Permutation#Algorithms_to_generate_permutations https://en.wikipedia.org/wiki/Permutation#Algorithms_to_gene... .. and there "Generation in lexicographic order" This algorithm only requires you to hold the last permutation in memory to obtain a new (distinct) one.