LeetCode（力扣）——Search in Rotated Sorted Array 搜索旋转排序数组 python实现

Posted 2020-11-13 hehe哒

题目描述：

python实现 Search in Rotated Sorted Array 搜索旋转排序数组  

　　中文：假设按照升序排序的数组在预先未知的某个点上进行了旋转。

　　( 例如，数组 [0,1,2,4,5,6,7] 可能变为 [4,5,6,7,0,1,2] )。

　　搜索一个给定的目标值，如果数组中存在这个目标值，则返回它的索引，否则返回 -1 。

　　你可以假设数组中不存在重复的元素。

　　你的算法时间复杂度必须是 O(log n) 级别。

　　英文：Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

Your algorithm‘s runtime complexity must be in the order of O(log n).

 

 1 class Solution(object):
 2     def search(self, nums, target):
 3         """
 4         :type nums: List[int]
 5         :type target: int
 6         :rtype: int
 7         """
 8         start = 0
 9         end = len(nums)-1
10         while start<=end:
11             mid = (start + end)/2   #对于整数会自动省去小数部分
12             if nums[mid] == target:
13                 return mid
14             if nums[mid]>=nums[start]:
15                 if target >= nums[start] and target<=nums[mid]:
16                     end = mid-1
17                 else:
18                     start = mid + 1
19                     
20             if nums[mid]<nums[end]:
21                 if target > nums[mid] and target<=nums[end]:
22                     start = mid+1
23                     
24                 else:
25                     end = mid -1
26         return -1

 

题目来源：力扣题库