class Solution {

public int pivotIndex(int[] nums) {

if(nums == null || nums.length == 0) return -1;

int len = nums.length;

int sum[] = new int[len + 1];

sum[0] = 0;

for(int i = 1; i <= len; i++){

sum[i] = sum[i - 1] + nums[i-1];

}

int res = -1;

for(int i = 0; i < len; i++){

if(sum[i] == sum[len] - sum[i+1]){

res = i;

break;

}

}

return res;

}

}