Golang Leetcode 645. Set Mismatch.go

func findErrorNums(nums []int) []int {

	m := make(map[int]int)
	sum := 0
	ret := make([]int, 2)
	for _, v := range nums {
		if _, ok := m[v]; ok {
			ret[0] = v
		} else {
			m[v] = 1
			sum += v
		}
	}
	l := len(nums)
	ret[1] = l*(1+l)/2 - sum
	return ret
}