leetcode 33. Search in Rotated Sorted Array

最新推荐文章于 2021-04-09 16:46:58 发布

头发结冰海鲜过敏的鱼

最新推荐文章于 2021-04-09 16:46:58 发布

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为便于理解应考虑的所有可能情况，作者通过画图简化问题。实际上需考虑四种情况，首先要看中间指针指向何处，然后考虑目标是在左半部分还是右半部分。

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In order to help me understand all the possible situations I should consider, I just draw a picture to make everything easier.
So acutally there are four situations we should consider, we should first see where middle pointer points at, and then consider whether target is in the left part or right part

class Solution(object):
    def search(self, nums, target):
        start = 0
        end = len(nums) - 1
        while start <= end:           
            middle = (start + end) // 2
            if nums[middle] == target: # if we find target
                return middle
            if nums[middle] > nums[end]: # in situation 1
                if target >= nums[start] and target < nums[middle]: # target in left part in situtation 1 
                    if target == nums[start]: return start
                    end = middle - 1
                else: # target in right part in situation 1
                    start = middle + 1
                    if start >= len(nums):
                        return -1
            else:# in situation 2
                if target >= nums[middle] and target <= nums[end]: # target in right part in situation 2
                    if target == nums[end]: return end
                    start = middle + 1
                else: # target in left part in situation 2
                    end = middle - 1
                    if end < 0:
                        return -1
        return -1