leetcode-go/easy/448.find-all-numbers-disappeared-in-an-array.go

func findDisappearedNumbers(nums []int) (res []int) {
	n := len(nums)
	set := make([]bool, n+1)
	for _, i := range nums {
		set[i] = true
	}
	for i := 1; i <= n; i++ {
		if !set[i] {
			res = append(res, i)
		}
	}
	return
}