leetcode 之Search in Rotated Sorted Array（三）

描述
    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.

二分法查找适用于排好序的，所以这题的关键是如何确定某部分的顺序是怎样的。

 int searchRotateSA(int A[], int n,int target)
 {
     int first = , last = n;
     while (first!=last)
     {
         int mid = first + (last - first) / ;
         if (A[mid] = target)
         {
             return mid;
         }
         else if (A[first]<=A[mid])//判断大小顺序
         {
             if (A[first] <= target&&target <= A[mid])
                 last = mid;
             else
                 first = mid + ;
         }
         else
         {
             if (A[first] >= target&& A[mid] <= target)
                 last = mid;
             else
                 first = mid + ;

         }
     }

     return -;
 }