033 search in rotated sorted array

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.

不要用语言自带的库来解决，这个就是用二分法实现的，还是来个实在的：

class Solution:
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        lo, hi = 0, len(nums) - 1
        while lo < hi:
            mid = (lo + hi) // 2
            if (nums[0] > target) ^ (nums[0] > nums[mid]) ^ (target > nums[mid]):
                lo = mid + 1
            else:
                hi = mid
        return lo if target in nums[lo:lo+1] else -1

这个异或用的实在是屌。。

再来个好理解的：

class Solution:
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        if not nums:
            return -1

        low, high = 0, len(nums) - 1

        while low <= high:
            mid = low + (high - low) // 2
            if target == nums[mid]:
                return mid

            if nums[low] <= nums[mid]:
                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