public class Solution
extends Object
1664 - Ways to Make a Fair Array\.
Medium
You are given an integer array `nums`. You can choose **exactly one** index ( **0-indexed** ) and remove the element. Notice that the index of the elements may change after the removal.
For example, if `nums = [6,1,7,4,1]`:
* Choosing to remove index `1` results in `nums = [6,7,4,1]`.
* Choosing to remove index `2` results in `nums = [6,1,4,1]`.
* Choosing to remove index `4` results in `nums = [6,1,7,4]`.
An array is **fair** if the sum of the odd-indexed values equals the sum of the even-indexed values.
Return the _**number** of indices that you could choose such that after the removal,_ `nums` _is **fair**._
**Example 1:**
**Input:** nums = [2,1,6,4]
**Output:** 1
**Explanation:**
Remove index 0: [1,6,4] -> Even sum: 1 + 4 = 5. Odd sum: 6. Not fair.
Remove index 1: [2,6,4] -> Even sum: 2 + 4 = 6. Odd sum: 6. Fair.
Remove index 2: [2,1,4] -> Even sum: 2 + 4 = 6. Odd sum: 1. Not fair.
Remove index 3: [2,1,6] -> Even sum: 2 + 6 = 8. Odd sum: 1. Not fair.
There is 1 index that you can remove to make nums fair.
**Example 2:**
**Input:** nums = [1,1,1]
**Output:** 3
**Explanation:** You can remove any index and the remaining array is fair.
**Example 3:**
**Input:** nums = [1,2,3]
**Output:** 0
**Explanation:** You cannot make a fair array after removing any index.
**Constraints:**
* 1 <= nums.length <= 105
* 1 <= nums[i] <= 104