33-Search in Rotated Sorted Array

题目：

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.

 

分析:

1.mid的位置判断，若A[mid]>=A[left],则mid在左边区域；若A[mid]<A[left],则mid在右边区域

2.如果mid在左边区域，当A[left]<=target<A[mid],right=mid-1;

3.如果mid在右边区域，当A[mid]<target<=A[right],left=mid+1;

public class Solution {
    public int search(int[] A, int target) {
        int left=0;
        int right=A.length-1;
        while(right>=left) {
            int mid=(right+left)/2;
            if(target==A[mid])
                return mid;
            if(A[mid]>=A[left]) {
                if(target>=A[left]&&target<A[mid]) {
                    right=mid-1;
                }else {
                    left=mid+1;
                }
            }else {
                if(target>A[mid]&&target<=A[right]) {
                    left=mid+1;
                }else {
                    right=mid-1;
                }
            }
        }
        return -1;
    }
}