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:

• <code>1 <= nums.length <= 10⁵</code>

• <code>1 <= numsi<= 10⁴</code>