search_in_rotated_sorted_array.py

"""

There is an integer array nums sorted in ascending order (with distinct values).

Prior to being passed to your function, nums is possibly rotated at an unknown pivot index k (1 <= 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). For example, [0,1,2,4,5,6,7] might be rotated at pivot index 3 and become [4,5,6,7,0,1,2].

Given the array nums after the possible rotation and an integer target, return the index of target if it is in nums, or -1 if it is not in nums.

You must write an algorithm with O(log n) runtime complexity.

 

Example 1:

Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4
Example 2:

Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1
Example 3:

Input: nums = [1], target = 0
Output: -1
 

Constraints:

1 <= nums.length <= 5000
-104 <= nums[i] <= 104
All values of nums are unique.
nums is an ascending array that is possibly rotated.
-104 <= target <= 104

"""

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        n = len(nums)
        left = 0
        right = n - 1

        while left <= right:
            mid = (left + right) // 2
            if target == nums[mid]:
                return mid

            # left sorted portion
            if nums[left] <= nums[mid]:
                if target > nums[mid] or target < nums[left]:
                    left = mid + 1
                else:
                    right = mid - 1

            # right sorted portion
            else:
                if target < nums[mid] or target > nums[right]:
                    right = mid - 1
                else:
                    left = mid + 1
        return -1