# Solving Leetcode Interviews in Seconds with AI: Ways to Make a Fair Array


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "1664" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like [Chatmagic](https://www.chatmagic.app), we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

	# Problem Statement
	> 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  

	# Explanation
	Here's the breakdown of the solution:

*   **Prefix Sums:** Calculate prefix sums for even and odd indices separately. This allows us to efficiently compute the sums of even and odd indices after removing an element.
*   **Iterate and Check:** Iterate through the array. For each index `i`, calculate the sums of even and odd indices of the array *after* removing the element at `i` using the precomputed prefix sums.
*   **Fairness Check:** Check if the even sum equals the odd sum after removal. Increment a counter if it's fair.

*   **Runtime Complexity:** O(n), where n is the length of the input array `nums`. **Storage Complexity:** O(n)

	
	# Code
	```python
	def waysToMakeFair(nums):
    n = len(nums)
    even_prefix = [0] * (n + 1)
    odd_prefix = [0] * (n + 1)

    for i in range(n):
        if i % 2 == 0:
            even_prefix[i + 1] = even_prefix[i] + nums[i]
            odd_prefix[i + 1] = odd_prefix[i]
        else:
            odd_prefix[i + 1] = odd_prefix[i] + nums[i]
            even_prefix[i + 1] = even_prefix[i]

    count = 0
    for i in range(n):
        even_sum = even_prefix[i] + (odd_prefix[n] - odd_prefix[i + 1])
        odd_sum = odd_prefix[i] + (even_prefix[n] - even_prefix[i + 1])

        if even_sum == odd_sum:
            count += 1

    return count
	```