724. 寻找数组的中心索引

class Solution {
public:
    int pivotIndex(vector<int> &nums) 
    {
        int total = accumulate(nums.begin(), nums.end(), 0);
        int sum = 0;
        for (int i = 0; i < nums.size(); ++i) 
        {
            if (2 * sum + nums[i] == total) 
            {
                return i;
            }
            sum += nums[i];
        }
        return -1;
    }
};