665. Non-decreasing Array

Medium

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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 can't get a non-decreasing array by modify at most one element.

Constraints:

• n == nums.length

• 1 <= n <= 104

• -105 <= nums[i] <= 105

class Solution:
    def checkPossibility(self, nums: List[int]) -> bool:
        spikes = 0
        for index in range(1, len(nums)):
            if nums[index-1] > nums[index]:
                spikes += 1
                # If this is 2nd index or value at 2-back index is also less than this current index
                if (index-2) < 0 or nums[index-2] <= nums[index]:
                    nums[index-1] = nums[index]
                else:
                    nums[index] = nums[index-1]
        return spikes <= 1