LeetCode in Kotlin

665. Non-decreasing Array

Medium

Given an array nums with n integers, your task is to check if it could become non-decreasing by modifying at most one element.

We define an array is non-decreasing if nums[i] <= nums[i + 1] holds for every i (0-based) such that (0 <= i <= n - 2).

Example 1:

Input: nums = [4,2,3]

Output: true

Explanation: You could modify the first 4 to 1 to get a non-decreasing array.

Example 2:

Input: nums = [4,2,1]

Output: false

Explanation: You cannot get a non-decreasing array by modifying at most one element.

Constraints:

• n == nums.length
• 1 <= n <= 104
• -105 <= nums[i] <= 105

Solution

class Solution {
    fun checkPossibility(nums: IntArray): Boolean {
        val n = nums.size
        if (n <= 2) {
            return true
        }

        var isModified = false
        for (i in 0..(n - 2)) {
            if (nums[i] <= nums[i + 1]) {
                continue
            }
            if (isModified) {
                return false
            }

            when {
                i == 0 || nums[i - 1] <= nums[i + 1] -> {
                    nums[i] = nums[i + 1]
                    isModified = true
                }
                i == n - 2 || nums[i] <= nums[i + 2] -> {
                    nums[i + 1] = nums[i]
                    isModified = true
                }
                else -> {
                    return false
                }
            }
        }
        return true
    }
}

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