#33. Search in Rotated Sorted Array

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.
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分析如下

889271574945197632.jpg

• 注意上图中的“实际又递归了函数”的意思是递归了“查找旋转数组”
• 另外两种情况，“查找顺序数组”

Python

# 非递归版  情况较多，不好理解
class Solution(object):
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        left = 0
        right = len(nums) - 1
        while  left <= right:
            mid = (left + right) // 2
            #print(mid, nums[mid])
            if nums[mid] == target:
                return mid
#这里需要判断mid在左半段还是右半段
#而不是判断target的大小关系
            elif nums[mid] < nums[right]: #nums[mid:right] sorted
                if nums[mid] <= target <= nums[right]:
                    left = mid + 1
                else:
                    right = mid - 1
            else:
                if nums[left] <= target <= nums[mid]:
                    right = mid - 1
                else:
                    left = mid + 1
        return -1

# 递归版
import sys
sys.setrecursionlimit(1500)
class Solution(object):
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        return self.searchFunc(nums, 0, len(nums)-1, target)
    
    def searchFunc(self, nums, left, right, target):
        mid = (left + right) // 2
        if nums[mid] == target:
            return mid
        elif nums[mid] < nums[right]:
            if nums[mid] <= target <= nums[right]:
                self.searchFunc(nums, mid+1, right, target)
            else:
                self.searchFunc(nums, left, mid-1, target)
        else:
            if nums[left] <= target <= nums[mid]:
                self.searchFunc(nums, left, mid-1, target)
            else:
                self.searchFunc(nums, mid+1, right, target)
        return -1

if __name__ == '__main__':
    a = [3, 4, 5, 6, 7, 0, 1, 2]
    b = [6, 7, 8, 1, 2, 3, 4, 5]
    t = 22

    p = Solution()
    print(p.search(a, t))