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
}