665. Non-decreasing Array

Given an array with n integers, your task is to check if it could become non-decreasing by modifying at most 1 element.

We define an array is non-decreasing if array[i] <= array[i + 1] holds for every i (1 <= i < n).

Example 1:

Input: [4,2,3]
Output: True
Explanation: You could modify the first 4 to 1 to get a non-decreasing array.

Example 2:

Input: [4,2,1]
Output: False
Explanation: You can't get a non-decreasing array by modify at most one element.

Note: The n belongs to [1, 10,000].

Solutions (Python)

1. Solution

class Solution:
    def checkPossibility(self, nums: List[int]) -> bool:
        flag = False
        for i in range(len(nums) - 1):
            if nums[i] > nums[i + 1]:
                if flag:
                    return False
                flag = True
                if i > 0 and nums[i - 1] > nums[i + 1]:
                    nums[i + 1] = nums[i]
        return True