33.搜索旋转排序数组.py

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# @lc app=leetcode.cn id=33 lang=python
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# [33] 搜索旋转排序数组
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# https://leetcode-cn.com/problems/search-in-rotated-sorted-array/description/
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# algorithms
# Medium (36.14%)
# Likes:    355
# Dislikes: 0
# Total Accepted:    43K
# Total Submissions: 119K
# Testcase Example:  '[4,5,6,7,0,1,2]\n0'
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# 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。
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# ( 例如，数组 [0,1,2,4,5,6,7] 可能变为 [4,5,6,7,0,1,2] )。
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# 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 。
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# 你可以假设数组中不存在重复的元素。
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# 你的算法时间复杂度必须是 O(log n) 级别。
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# 示例 1:
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# 输入: nums = [4,5,6,7,0,1,2], target = 0
# 输出: 4
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# 示例 2:
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# 输入: nums = [4,5,6,7,0,1,2], target = 3
# 输出: -1
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class Solution(object):
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        low=0
        high=len(nums)-1
        while low<=high:
            mid=low+(high-low)/2
            if nums[mid]==target:
                return mid
            if nums[mid]>=nums[low]:
                if nums[low]<=target<=nums[mid]:
                    high=mid-1
                else:
                    low=mid+1
            else:
                if nums[mid]<=target<=nums[high]:
                    low=mid+1
                else:
                    high=mid-1
        return -1