665 非递减数列

三种情况：

1、nums=[4,2,5]，nums[i]<nums[i-1]，此时只需要改变nums[i-1]，[1,2,5]

2、nums=[1,4,2,5]，i>.1，nums[i]<nums[i-1]，此时调整nums[i-1]，满足nums[i-2]<=nums[i-1]<=nums[i]，[1,2,2,5]

3、nums=[3,4,2,5]，i>.1，nums[i-2]>nums[i]，此时调整nums[i-1]不行，只能让nums[i]=nums[i-1]，[3,4,4,5]

 1 def checkPossibility(nums):
 2     N = len(nums)
 3     count = 0
 4     for i in range(1, N):
 5         if nums[i] < nums[i - 1]:
 6             count += 1
 7             if i == 1 or nums[i] >= nums[i - 2]:
 8                 nums[i - 1] = nums[i]
 9             else:
10                 nums[i] = nums[i - 1]
11     print(nums)
12     return count <= 1