64 lines
1.2 KiB
Go
64 lines
1.2 KiB
Go
|
package sorting
|
||
|
|
|
||
|
|
import (
|
||
|
|
"math/rand"
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
func exch[T any](items []T, a int, b int) {
|
||
|
|
items[a], items[b] = items[b], items[a]
|
||
|
|
}
|
||
|
|
|
||
|
|
func partition[T any](items []T, lo int, hi int, less func(a, b T) bool) int {
|
||
|
|
i, j := lo, hi+1
|
||
|
|
v := items[lo]
|
||
|
|
|
||
|
|
for {
|
||
|
|
for i++; less(items[i], v); i++ {
|
||
|
|
if i == hi {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for j--; less(v, items[j]); j-- {
|
||
|
|
if j == lo {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if i >= j {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
|
||
|
|
exch(items, i, j)
|
||
|
|
}
|
||
|
|
exch(items, j, lo)
|
||
|
|
|
||
|
|
return j
|
||
|
|
}
|
||
|
|
|
||
|
|
func doQuickSort[T any](items []T, lo int, hi int, less func(a, b T) bool) {
|
||
|
|
if hi-lo <= 15 {
|
||
|
|
Insertion(items[lo:hi+1], less)
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
if lo >= hi {
|
||
|
|
return
|
||
|
|
}
|
||
|
|
mi := partition(items, lo, hi, less)
|
||
|
|
doQuickSort(items, lo, mi-1, less)
|
||
|
|
doQuickSort(items, mi+1, hi, less)
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
func Quick[T any](items []T, less func(a, b T) bool) {
|
||
|
|
|
||
|
|
// We shuffle array to prevent worst case scenario when array already sorted.
|
||
|
|
// Without shuffling we get O(n^2) time. Another variant how to prevent
|
||
|
|
// such performance drop is to compute median element in partition function.
|
||
|
|
rand.Seed(time.Now().UnixNano())
|
||
|
|
rand.Shuffle(len(items), func(i, j int) { items[i], items[j] = items[j], items[i] })
|
||
|
|
doQuickSort(items, 0, len(items)-1, less)
|
||
|
|
}
|