scratch/algos/quicksort.go (view raw)
| 1 | package algos |
| 2 | |
| 3 | func partition(inp []int, lo, hi int) int { |
| 4 | pivot := inp[hi] // might result in O(n^2) |
| 5 | |
| 6 | idx := lo - 1 |
| 7 | for i := lo; i < hi; i++ { |
| 8 | if inp[i] <= pivot { |
| 9 | idx++ |
| 10 | inp[i], inp[idx] = inp[idx], inp[i] |
| 11 | } |
| 12 | } |
| 13 | |
| 14 | idx++ |
| 15 | inp[hi], inp[idx] = inp[idx], pivot |
| 16 | return idx |
| 17 | } |
| 18 | |
| 19 | func qs(inp []int, lo, hi int) { |
| 20 | if lo >= hi { |
| 21 | return |
| 22 | } |
| 23 | |
| 24 | pivot := partition(inp, lo, hi) |
| 25 | qs(inp, lo, pivot-1) |
| 26 | qs(inp, pivot+1, hi) |
| 27 | } |
| 28 | |
| 29 | func QuickSort(input []int) { qs(input, 0, len(input) - 1) } |