LeetCode - 448 - Find All Numbers Disappeared in an Array

Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.

Find all the elements of [1, n] inclusive that do not appear in this array.

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

Example:

Input:
[4,3,2,7,8,2,3,1]

Output:
[5,6]

跟442思路一毛一样，唔，那为喵一个是easy一个是medium (⊙v⊙)

目测自己掌握了做法，不知道能不能举一反三【托腮】

class Solution {
public:
vector<int> findDisappearedNumbers(vector<int>& nums) {
vector<int> ans;
for (int i = 0; i < nums.size(); ) {
if (nums[i] != nums[nums[i] - 1]) swap(nums[i], nums[nums[i] - 1]);
else ++i;
}
for (int i = 0; i < nums.size(); ++i) {
if (nums[i] != i + 1) ans.push_back(i + 1);
}
return ans;
}
};