题解 | 相等的草堆

1. 前后缀和

import java.util.*;


public class Solution {
    public int pivotIndex (int[] nums) {
        final int n = nums.length;
        int[] left = new int[n];
        int[] right = new int[n];
        left[0] = 0;
        for (int i = 1; i < n; ++i) {
            left[i] = left[i - 1] + nums[i - 1];
        }
        right[n - 1] = 0;
        for (int i = n - 2; i >= 0; --i) {
            right[i] = right[i + 1] + nums[i + 1];
        }

        for (int i = 0; i < n; ++i) {
            if (left[i] == right[i]) {
                return i;
            }
        }
        return -1;
    }
}