1752. check if array is sorted and rotated

Given an array nums, return true if the array was originally sorted in non-decreasing order, then rotated some number of positions (including zero). Otherwise, return false.

There may be duplicates in the original array.

Note: An array A rotated by x positions results in an array B of the same length such that A[i] == B[(i+x) % A.length], where % is the modulo operation.

solutions

Just remember edge cases for monotone, single value.

def check(self, nums: List[int]) -> bool:
	"""
	- iterate, adjacent elements must be non-decreasing (allow one decreasing)
	  
	- if we saw monotone, return True
	- if we saw no decreasing, nums[0] < nums[-1]
	- if we saw one decreasing, nums[0] >= nums[-1]
	  
	- special case monotone array (track if we see change at all?)
	"""
	if len(nums) == 1:
		return True
	  
	is_monotone = True
	num_decreasing = 0
	for v1, v2 in zip(nums[:-1], nums[1:]):
		if v1 != v2: is_monotone = False
		if v1 < v2:
			is_monotone = False
		elif v1 > v2:
			if num_decreasing > 0:
				return False
			num_decreasing += 1
 
	if is_monotone:
		return True
	return nums[0] < nums[-1] if num_decreasing == 0 else nums[0] >= nums[-1]