Non-decreasing Array.py

class Solution:
    def checkPossibility(self, nums: List[int]) -> bool:
        unstable=0
        for i in range(1,len(nums)):
            if nums[i]<nums[i-1]:
                unstable+=1
                if i<2 or nums[i-2]<=nums[i]:
                    nums[i-1]=nums[i]
                else:
                    nums[i]=nums[i-1]
                
                if unstable>1:
                    return False
        return True