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leetcode No81. Search in Rotated Sorted Array II

时间:2016-08-06 21:59:17      阅读:123      评论:0      收藏:0      [点我收藏+]

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Question:

Follow up for "Search in Rotated Sorted Array":
What if duplicates are allowed?

Would this affect the run-time complexity? How and why?

Write a function to determine if a given target is in the array.

在旋转数组中找target,与I不同的是,这次存在重复元素

Algorithm:

先找顺序,再找target
有三种情况:(至少有一半是顺序的)
1、nums[mid]==target
2、nums[l]<nums[mid](左半是顺序,如果target在范围内,二分,如果不在,则在右半找顺序,即重复1,2,3)
3、nums[l]>nums[mid](右半是顺序,如果target在范围内,二分,如果不在,则在左半找顺序,则重复1,2,3) 
4、nums[l]>nums[mid](不确定左边是否为重复,只能往前一步 

Accepted Code:

class Solution {
public:
    bool search(vector<int>& nums, int target) {
        int res=-1;
        int l=0;
        int r=nums.size()-1;
        int mid=0;
        while(l<=r)
        {
            int mid=l+(r-l)/2;
            if(nums[mid]==target)
                return true;
            else if(nums[l]<nums[mid])          //mid左边是顺序
            {
                if(nums[l]<=target&&nums[mid-1]>=target)   
                    r=mid-1;
                else
                    l=mid+1;
            }
            else if(nums[l]>nums[mid])         //mid右边是顺序
            {
                if(nums[mid+1]<=target&&nums[r]>=target)   
                    l=mid+1;
                else 
                    r=mid-1;
            }
            else              //不确定左边是否为重复,只能往前一步
                l++;
        }
        if(nums[mid]==target)
            return true;
        else 
            return false;        
    }
};





leetcode No81. Search in Rotated Sorted Array II

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原文地址:http://blog.csdn.net/u011391629/article/details/52138430

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