Quicksort's space complexity

[mamigot]

O(log(n)) instead of O(n)
http://stackoverflow.com/questions/12573330/why-does-quicksort-use-ologn-extra-space

[mxj4]

Yes it should be O(log(n)), please fix.

[bbodenmiller]

@ericdrowell I think this should be merged before the others.

[BartMassey]

Quicksort is O(n) worst case space complexity unless you are clever about it. The worst case is the case in which the time complexity is n^2 because pivots have been chosen poorly: there will be n levels of recursion, each with its own pivot point stored, so n auxiliary storage. Sedgewick discusses the use of tail-call on the larger partition to eliminate these stack frames, making the worst-case storage O(log n), but I've never seen anybody implement it like that in practice: if you aren't getting the average case O(log n) time complexity out of Quicksort, the extra storage is the least of your worries.