138. 子数组之和 map存储加规律

vector<int> subarraySum(vector<int> nums){  
        // write your code here  
        int sum = 0;  
        vector<int> ret;  
        unordered_map<int, int> map;  
        map[0] = -1;    //这个是把0先加进去了，
        for(int i=0; i<nums.size();i++)  
        {  
           sum += nums[i];  
             
           if(map.find(sum) != map.end())  
           {    cout<<map.find(sum)->first<<endl;
               ret.push_back(map[sum] +1);  
               ret.push_back(i);  
               return ret;  
           }  
  
           map[sum] = i;  
     
        }  
    
        return ret;  
    }