Search in Rotated Sorted Array

Suppose a sorted array 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.

时间复杂度O(n)
public int search(int[] A, int target) {
for(int i=0;i<A.length;i++){
if(target==A[i])
return i;
}
return -1;
}

二分法：

public class Solution {

public int search(int[] A,int target){
int first=0,mid,last=A.length;
while(first!=last){
mid=(first+last)/2;
if(target==A[mid])return mid;
if (A[first] <= A[mid]) {
if (A[first] <= target && target < A[mid])//有序部分
last = mid;
else
first = mid + 1;
} else {
if (A[mid] < target && target <= A[last-1])//有序部分
first = mid + 1;
else
last = mid;
}
}
return -1;
}
}