724. Find the central subscript of the array

Original link ：724. Find the central subscript of the array

 

solution:

        Left summation *2+ Central index value = The sum of the  

class Solution {
public:
    int pivotIndex(vector<int>& nums) {
        int sum = 0;
        for(auto &x : nums) sum += x;   // Find the sum 
        int k = 0;
        for(int i = 0;i < nums.size();i++) {
            if(i + 1 <= nums.size() && (k * 2 + nums[i] == sum)) return i;   
            k += nums[i];
        }
        
        return -1;
    }
};