Longest Strictly Increasing or Strictly

Tested Python solution for LeetCode 3105 with 16 pytest cases. Generate a practice environment with lcpy.

LeetCode 3105, Easy. Topics: Array. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 16 parametrized pytest cases, and a playground notebook:

lcpy gen -n 3105   # by problem number
lcpy gen -s longest_monotonic_subarray   # by problem name

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Problem

You are given an array of integers nums. Return the length of the longest subarray of nums which is either strictly increasing or strictly decreasing.

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Examples

Input: nums = [1,4,3,3,2]
Output: 2
Explanation:
The strictly increasing subarrays of nums are [1], [2], [3], [3], [4], and [1,4].
The strictly decreasing subarrays of nums are [1], [2], [3], [3], [4], [3,2], and [4,3].
Hence, we return 2.

Input: nums = [3,3,3,3]
Output: 1
Explanation:
The strictly increasing subarrays of nums are [3], [3], [3], and [3].
The strictly decreasing subarrays of nums are [3], [3], [3], and [3].
Hence, we return 1.

Input: nums = [3,2,1]
Output: 3
Explanation:
The strictly increasing subarrays of nums are [3], [2], and [1].
The strictly decreasing subarrays of nums are [3], [2], [1], [3,2], [2,1], and [3,2,1].
Hence, we return 3.

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Constraints

• 1 <= nums.length <= 50
• 1 <= nums[i] <= 50

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(n)
    # Space: O(1)
    def longest_monotonic_subarray(self, nums: list[int]) -> int:
        best = 1
        inc = dec = 1
        for i in range(1, len(nums)):
            if nums[i] > nums[i - 1]:
                inc += 1
                dec = 1
            elif nums[i] < nums[i - 1]:
                dec += 1
                inc = 1
            else:
                inc = dec = 1
            best = max(best, inc, dec)
        return best

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Complexity

Time	Space
O(n)	O(1)

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Tags

NeetCode All.