665. Non-decreasing Array

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

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

💻 Lời Giải

Python 0665-non-decreasing-array.py 
class Solution:
    def checkPossibility(self, nums: List[int]) -> bool:
        cnt = 0
        n = len(nums)
        
        for i in range(1, n):
            if nums[i - 1] > nums[i]:
                if cnt == 1:
                    return False
                cnt += 1
                if i - 2 < 0 or nums[i - 2] <= nums[i]:
                    nums[i - 1] = nums[i]
                else:
                    nums[i] = nums[i - 1]
        
        return True