Leetcode_c++： Search in Rotated Sorted Array II (081）

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.

算法

二分查找

O（lgn）

class Solution {
public:
bool search(vector<int>& A, int target) {
int n=A.size();
int left=0,right=n;
while(left!=right){
int mid=(left+right)/2;
if(A[mid]==target)
return  true;
if(A[mid]>A[left]) //[left~mid] is unrotated sorted
{
if(A[left]<=target && target <A[mid])
right=mid;
else
left=mid+1;
}else if(A[mid]<A[left]) // 【mid-right】 is unordered sorted
{
if(A[mid]<target && target<=A[right-1])
left=mid+1;
else
right=mid;
}else
left++;
}
return false;

}
};