[코테] 리트코드 이진 검색 33. Search in Rotated Sorted Array

33. Search in Rotated Sorted Array

문제 링크

https://leetcode.com/problems/search-in-rotated-sorted-array/description/

문제 설명

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.

제한 사항

• 1 <= nums.length <= 5000
• -10^4 <= nums[i] <= 10^4
• All values of nums are unique.
• nums is an ascending array that is possibly rotated.
• -10^4 <= target <= 10^4

입출력 예 #1

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

입출력 예 #2

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

입출력 예 #3

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

문제 풀이

1. 이진 검색을 이용한 target 찾는 풀이
2. 파이썬 내장함수를 이용한 target 찾는 풀이

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        # 예외 처리
        if not nums:
            return -1

        # 최솟값을 찾아 피벗 설정
        left, right = 0, len(nums) - 1
        while left < right:
            mid = left + (right - left) // 2

            if nums[mid] > nums[right]:
                left = mid + 1
            else :
                right = mid

        pivot = left

        # 피벗 기준 이진 검색
        left, right = 0, len(nums) - 1
        while left <= right:
            mid = left + (right - left) // 2
            mid_pivot = (mid + pivot) % len(nums)

            if nums[mid_pivot] < target:
                left = mid + 1
            elif nums[mid_pivot] > target:
                right = mid - 1
            else:
                return mid_pivot

        return -1

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        try: 
            return nums.index(target)
        except:
            return -1