Function partition

search/selectk.go:22–32

(array []int, l, r int)

}

func partition(array []int, l, r int) int {
	elem, j := array[l], l+1
	for i := l + 1; i < r; i++ {
		if array[i] <= elem {
			array[i], array[j] = array[j], array[i]
			j++
		}
	}
	array[l], array[j-1] = array[j-1], array[l]
	return j - 1
}