1991. Find the Middle Index in Array

class Solution {
public:
    int findMiddleIndex(vector<int>& nums) {
        int sum=0;
       for(auto it:nums){
          sum+=it;
       }
       int leftsum=0;
       for(int i=0;i<nums.size();i++){
          if(leftsum==sum-leftsum-nums[i]){   //13 
            return i;
          }
          leftsum+=nums[i];
       }
       return -1;

    }
};