LeetCode in Kotlin

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

Solution

class Solution {
    fun waysToMakeFair(nums: IntArray): Int {
        var res = 0
        val even = IntArray(nums.size)
        val odd = IntArray(nums.size)
        var oddSum = 0
        var evenSum = 0
        for (i in nums.indices) {
            if (i % 2 == 0) {
                evenSum += nums[i]
            } else {
                oddSum += nums[i]
            }
            even[i] = evenSum
            odd[i] = oddSum
        }
        for (i in nums.indices) {
            if (i == 0) {
                evenSum = odd[nums.size - 1] - odd[0]
                oddSum = even[nums.size - 1] - even[0]
            } else {
                oddSum = odd[i - 1] + even[nums.size - 1] - even[i]
                evenSum = even[i - 1] + odd[nums.size - 1] - odd[i]
            }
            if (evenSum == oddSum) {
                res++
            }
        }
        return res
    }
}

This site is open source. Improve this page.