leetcode 1. Two Sum

class Solution {public:        vector<int> twoSum(vector<int>& nums, int target) {       vector<int> ans;       map<int,int> m;       for(int i = 0;i < nums.size() ;i++){           if(m.find(target-nums[i]) != m.end()){               ans.push_back(m[target-nums[i]]);               ans.push_back(i);               return ans;           }           m[nums[i]] = i;       }       return ans;    }};