package q3354

func countValidSelections(nums []int) int {
	sumR := 0
	for i := range nums {
		sumR += nums[i]
	}

	sumL := 0
	nValid := 0
	for i := range nums {
		sumR -= nums[i]
		if i > 0 {
			sumL += nums[i-1]
		}
		if nums[i] == 0 {
			diff := sumL - sumR
			if diff == 0 {
				nValid += 2
			} else if diff*diff == 1 {
				nValid++
			}
		}
	}
	return nValid
}

var _ = countValidSelections