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package sort
import (
"algorithms/ds"
)
func Quick(a ds.ArrayList) ds.ArrayList {
a = Shuffle(a)
quick(a, 0, len(a)-1)
return a
}
func quick(a ds.ArrayList, lo, hi int) {
if hi <= lo {
return
}
j := quickPartition(a, lo, hi)
quick(a, lo, j-1)
quick(a, j+1, hi)
}
func quickPartition(a ds.ArrayList, lo, hi int) int {
i := lo // Left scan index
j := hi+1 // Right scan index
v := a[lo] // Partitioning item
for {
// Scan left
for {
i++
if i == hi {
break
}
if a[i].Lower(v) {
continue
}
break
}
// Scan right
for {
j--
if j == lo {
break
}
if v.Lower(a[j]) {
continue
}
break
}
// Check scan complete
if i >= j {
break
}
a.Swap(i, j)
}
// Put partitioning item v into a[j]
a.Swap(lo, j)
// whith a[lo..j-1 <= a[j] <= a[j+1..hi]
return j
}
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