Leetcode Note: Go - Binary Watch

var ans []string
var arr = []int{8, 4, 2, 1, 32, 16, 8, 4, 2, 1}

func readBinaryWatch(turnedOn int) []string {
	ans = []string{}
	backtrack(turnedOn, 0, 0, 0)
	return ans
}

func backtrack(turnedOn int, H int, M int, k int) {

	if turnedOn == 0 {
		Hs, Ms := strconv.Itoa(H), strconv.Itoa(M)
		if M < 10 {
			Ms = "0" + Ms
		}
		ans = append(ans, Hs+":"+Ms)
		return
	}

	for i := k; i < 10; i++ {
		h, m := H, M

		if i < 4 {
			h += arr[i]
		} else {
			m += arr[i]
		}

		if h < 12 && m < 60 {
			backtrack(turnedOn-1, h, m, i+1)
		}

	}
}