0724-find-pivot-index.adoc

724. Find Pivot Index

{leetcode}/problems/find-pivot-index/[LeetCode - Find Pivot Index^]

Given an array of integers nums, write a method that returns the "pivot" index of this array.

We define the pivot index as the index where the sum of the numbers to the left of the index is equal to the sum of the numbers to the right of the index.

If no such index exists, we should return -1. If there are multiple pivot indexes, you should return the left-most pivot index.

Example 1:

Input:
nums = [1, 7, 3, 6, 5, 6]
Output: 3
Explanation:
The sum of the numbers to the left of index 3 (nums[3] = 6) is equal to the sum of numbers to the right of index 3.
Also, 3 is the first index where this occurs.

Example 2:

Input:
nums = [1, 2, 3]
Output: -1
Explanation:
There is no index that satisfies the conditions in the problem statement.

Note:

• The length of nums will be in the range [0, 10000].

• Each element nums[i] will be an integer in the range [-1000, 1000].

思路分析

这道题的技巧和 238. Product of Array Except Self 类似。

看答案，也可以直接求和，然后在依次相加减得到两边的和。

一刷

link:{sourcedir}/_0724_FindPivotIndex.java[role=include]

参考资料

1. 724. 寻找数组的中心下标 - 前缀和，清晰图解