Search in Rotated Sorted Array II — LeetCode 81 Python Solution

The problem

There is an integer array nums sorted in non-decreasing order (not necessarily with distinct values). Before being passed to your function, nums is rotated at an unknown pivot index k (0 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]] (0-indexed).

Example

Input

nums = [2,5,6,0,0,1,2], target = 0

Output

true

Python solution

class Solution:
    def search(self, nums: List[int], target: int) -> bool:
        n = len(nums)
        l, r = 0, n - 1
        while l < r:
            mid = (l + r) >> 1
            if nums[mid] > nums[r]:
                if nums[l] <= target <= nums[mid]:
                    r = mid
                else:
                    l = mid + 1
            elif nums[mid] < nums[r]:
                if nums[mid] < target <= nums[r]:
                    l = mid + 1
                else:
                    r = mid
            else:
                r -= 1
        return nums[l] == target

Complexity

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 81. Search in Rotated Sorted Array II is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The monotonic stack guide has the Python template for the pattern and the 225 LeetCode problems that use it.

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