Function quickSort

topics/go/algorithms/sorting/quick/quick.go:8–22

quickSort is an in-place sorting algorithm. It takes a random list of numbers, and uses the `recursive` process to divides it into partitions then sorts those. - Time complexity O(nlog n) - Space complexity O(log n)

(randomList []int, leftIdx, rightIdx int)

// - Time complexity O(nlog n)
// - Space complexity O(log n)
func quickSort(randomList []int, leftIdx, rightIdx int) []int {
	switch {
	case leftIdx > rightIdx:
		return randomList

	// Divides array into two partitions.
	case leftIdx < rightIdx:
		randomList, pivotIdx := partition(randomList, leftIdx, rightIdx)

		quickSort(randomList, leftIdx, pivotIdx-1)
		quickSort(randomList, pivotIdx+1, rightIdx)
	}

	return randomList
}

// partition it takes a portion of an array then sort it.
func partition(randomList []int, leftIdx, rightIdx int) ([]int, int) {