Quicksort is a sorting algorithm invented by C
Shellsort is a sorting algorithm that is a modification of insertion sort in which elements are compared across gaps of different sizes.
If you use shellsort no extra memory is needed at all though shellsort will be much slower than quicksort
Algorithm for counting the number of unique colors in an image
If worst case is critical just don t use quicksort;shellsort has a better upperbound
Regarding Quick Sort Killer