1 Two Sum

 1 class Solution 
 2 {
 3 public:
 4     vector<int> twoSum(vector<int>& nums, int target) 
 5     {
 6         unordered_map<int,int> hash;
 7         for(int i=0;i<nums.size();i++)
 8         {   
 9             if(hash.find(target-nums[i])!=hash.end())
10                 return vector<int> {hash[target-nums[i]],i};
11             hash[nums[i]]=i;
12         }
13     }
14 };