448. Find All Numbers Disappeared in an Array

Medium

Given an array nums of n integers where nums[i] is in the range [1, n], return an array of all the integers in the range [1, n] that do not appear in nums.

Example 1:

Input: nums = [4,3,2,7,8,2,3,1]
Output:
 [5,6]

Example 2:

Input: nums = [1,1]
Output:
 [2]

Constraints:

• n == nums.length

• 1 <= n <= 105

• 1 <= nums[i] <= n

Follow up: Could you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.

解題

func findDisappearedNumbers(nums []int) []int {
    l := len(nums)
    exist := make([]bool, l)

    for _, num := range nums {
        exist[num - 1] = true
    }

    ans := make([]int, 0)
    for i, n := range exist {
        if !n { ans = append(ans, i+1) }
    }

    return ans
}