leetcode 题解：Search in Rotated Sorted Array II （旋转已排序数组查找2）

题目：

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.

说明：

1）和1比只是有重复的数字，整体仍采用二分查找

2）方法二 ：

实现：

   一、我的实现：

 1 class Solution {
 2 public:
 3     bool search(int A[], int n, int target) {
 4         if(n==0||n==1&&A[0]!=target) return false;
 5         if(A[0]==target) return true;
 6         int i=1;
 7         while(A[i-1]<=A[i])  i++;
 8
 9         bool pre=binary_search(A,0,i,target);
10         bool pos=binary_search(A,i,n-i,target);
11         return pre==false?pos:pre;
12     }
13 private:
14     bool binary_search(int *B,int lo,int len,int goal)
15     {
16         int low=lo;
17         int high=lo+len-1;
18         while(low<=high)
19         {
20             int middle=(low+high)/2;
21             if(goal==B[middle])//找到，返回index
22                return true;
23             else if(B[middle]<goal)//在右边
24                low=middle+1;
25             else//在左边
26                high=middle-1;
27         }
28         return false;//没有，返回-1
29     }
30 };

二、网上开源实现：

 1 class Solution {
 2 public:
 3     bool search(int A[], int n, int target) {
 4          int low=0;
 5          int high=n-1;
 6          while(low<=high)
 7          {
 8             const int middle=(low+high)/2;
 9             if(A[middle]==target) return true;
10             if(A[low]<A[middle])
11             {
12                if(A[low]<=target&&target<A[middle])
13                   high=middle-1;
14                else
15                   low=middle+1;
16             }
17             else if(A[low]>A[middle])
18             {
19                if(A[middle]<target&&target<=A[high])
20                   low=middle+1;
21                else
22                   high=middle-1;
23             }
24             else
25                 low++;
26          }
27          return false;
28     }
29 };

leetcode 题解：Search in Rotated Sorted Array II （旋转已排序数组查找2）,布布扣,bubuko.com