leetcode:Search in Rotated Sorted Array

题目要求：

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.

题目地址：https://leetcode.com/problems/search-in-rotated-sorted-array/

 

public class Solution {
    public static int search(int[] A, int target) {
            int first=0,last=A.length-1,mid;
            while(first<=last){
                mid=(first+last)/2;
                System.out.println("当前搜索范围"+A[first]+"--"+A[last]+",mid="+A[mid]);
                if(A[mid]==target)return mid;
                else if(A[first]<=A[mid]){//左有序
                    
                    if(target<A[first]||target>A[mid]){
                        
                        first=mid+1;
                    }else{
                        last=mid-1;
                    }
                }else{//右有序
                    if(target<A[mid]||target>A[last]){
                        last=mid-1;
                    }else{
                        first=mid+1;
                    }
                    
                }
            }
            return -1;
        }
}

POINTS：和传统2分查找无差别，只是通过A[mid]与A[first]A[last]的大小比较确定翻转的奇异点在2段范围中的哪一段，在对正常有序的那一段判断下目标在不在其中。