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Ways to Make a Fair Array

You are given an integer array nums.

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]:

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.

Ways to Make a Fair Array diagram

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 <= 10^5
  • 1 <= nums[i] <= 10^4

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