寻找数组的中心下标
class Solution { public: int pivotIndex(vector<int>& nums) { int result = -1; int sum = 0 , left_sum=0; for(int it:nums) sum += it; for(int i=0 ; i<nums.size() ;i++) { if((sum-nums[i])%2 ==0 && (sum-nums[i])/2 == left_sum ) return i; else left_sum += nums[i]; } return result; } };