class Solution {
    public int pivotIndex(int[] nums) {
        int n = nums.length;

        if(n == 1) {
            return 0;
        }

        /*int leftSum, rightSum;
        for(int idx = 0; idx < n; idx++) {
            leftSum = 0;
            rightSum = 0;
            for(int left = 0; left < idx; left++) {
                leftSum += nums[left];
            }
            for(int right = idx + 1; right < n; right++) {
                rightSum += nums[right];
            }
            if(leftSum == rightSum) return idx;
        }

        return -1;*/
        int totalSum = 0;
        for(int num : nums) {
            totalSum += num;
        }

        int leftSum = 0, rightSum;

        for(int idx = 0; idx < n; idx++) {
            rightSum = totalSum - leftSum - nums[idx];
            if(leftSum == rightSum) return idx;
            leftSum += nums[idx];
        }
        
        return -1;
    }
}