leetcode 之Sum系列（七）

 vector<int> twoSum(vector<int> &num, int target)
      {
          unordered_map<int, int> mapping;
          vector<int> result;
          for (int i = 0; i < num.size(); i++)
              mapping[num[i]] = i;

          for (int i = 0; i < num.size(); i++)
          {
              int gap = target - num[i];
              //第二个判断条件更准确的是mapping[gap]！=i，防止选到自身
              if (mapping.find(gap) != mapping.end()&&mapping[gap]>i)
              {
                  result.push_back(i + 1);
                  result.push_back(mapping[gap] + 1);
                  break;
              }
          }

          return result;
      }