Leetcode 1 Two Sum STL

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){
            m[nums[i]] =  i;
        }
        for(int i = 0; i < nums.size(); ++i){
            if(m.find(target - nums[i]) != m.end() && m[target - nums[i]]!= i){
                ans.push_back(i);
                ans.push_back(m[target - nums[i]]);
                break;
            }
        }
        return ans;
    }
};