448.cpp

class Solution {
public:
    vector<int> findDisappearedNumbers(vector<int>& nums) {
        vector<int> result;
        for(int i = 0; i < nums.size(); i++) {
            int m = abs(nums[i]) - 1;
            nums[m] = nums[m] > 0 ? -nums[m] : nums[m];
        }
        for(int j = 0; j < nums.size(); j++) {
            if (nums[j] > 0) result.push_back(j+1);
        }
        return result;
    }
};