25 March.cpp

class Solution {
public:
    vector<int> findDuplicates(vector<int>& nums) {
        vector<int>ans;
        int n = nums.size();
        for(int i = 0; i < n ; i++){
            int index = abs(nums[i]) - 1;
            if(nums[index] < 0){
               ans.push_back(index+1);
            }else{
                nums[index] = -nums[index];
            }
        }

        return ans;

    }
};