448. 找到所有数组中消失的数字

class Solution {
public:
    vector<int> findDisappearedNumbers(vector<int>& nums) {
        for(auto num : nums) {
            if(nums[abs(num) - 1] >= 0) nums[abs(num) - 1] *= -1;
        }
        vector<int> ans;
        for(int ii = 0; ii < nums.size(); ii++) {
            if(nums[ii] > 0) ans.push_back(ii + 1);
        }
        return ans;
    }
};