mountain_array_valid.py

"""
https://leetcode.com/problems/find-in-mountain-array/
"""
import unittest
from typing import List


def valid(nums: List[int]) -> bool:
 length = len(nums)
 if length < 3:
 return False
 # 是否单调递增
 last_item_is_increasing = nums[0] < nums[1]
 if not last_item_is_increasing:
 return False
 for i in range(2, length):
 if nums[i-1] > nums[i]:
 last_item_is_increasing = False
 elif nums[i-1] < nums[i]:
 # 山脉数组不允许先递减(False)后递增(True)
 if not last_item_is_increasing:
 return False
 last_item_is_increasing = True
 else:
 return False
 if not last_item_is_increasing:
 return True
 else:
 return False


class UnitTest(unittest.TestCase):
 TEST_CASES = [
 ([2, 1], False),
 ([3, 5, 5], False),
 ([0, 3, 2, 1], True),
 ]

 def test_valid(self):
 for nums, expected in self.TEST_CASES:
 self.assertEqual(expected, valid(nums))