vector<int> twoSum(vector<int>& nums, int target)

 {

     unordered_map<int, int> numsHash;

     vector<int> res;

     for (int i = ; i < nums.size(); ++i) {

         int num_last = target - nums[i];

         if (numsHash.find(num_last) != numsHash.end()) {

             res.push_back(numsHash[num_last] + );

             res.push_back(i + );

             break;

         } else {

             numsHash[nums[i]] = i;

         }

     }

     return res;

 }

 vector<int> twoSum(vector<int>& nums, int target)

 {

     vector<int> res;

     int lpos = , rpos = nums.size() - ;

     sort(nums.begin(), nums.end());

     while (lpos < rpos) {

         int num = nums[lpos] + nums[rpos];

         if (num == target) {

             res.push_back(lpos + );

             res.push_back(rpos + );

         } else if (num > target) {

             rpos--;

         } else {

             lpos++;

         }

     }

     return res;

 }