Find the Middle Index in Array
Given a 0-indexed integer array nums, find the leftmost middleIndex, which is the smallest among all possible valid indices.
A middleIndex is an index where the sum of the elements to its left is equal to the sum of the elements to its right:
nums[0] + nums[1] + ... + nums[middleIndex - 1] == nums[middleIndex + 1] + nums[middleIndex + 2] + ... + nums[nums.length - 1]
If middleIndex == 0, the left side sum is considered to be 0. Similarly, if middleIndex == nums.length - 1, the right side sum is considered to be 0.
Return the leftmost middleIndex that satisfies the condition, or -1 if there is no such index.
Note: This question is the same as 724: https://leetcode.com/problems/find-pivot-index/
Example 1
Input
nums = [2,3,-1,8,4]Output
3The sum before index 3 is 2 + 3 + -1 = 4, and the sum after index 3 is 4.
Example 2
Input
nums = [1,-1,4]Output
2The sum before index 2 is 1 + -1 = 0, and the sum after index 2 is 0.
Constraints
- 1 <= nums.length <= 100
- -1000 <= nums[i] <= 1000