Search in Rotated Sorted Array leetcode java

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.
分析
二分查找，难度主要在于左右边界的确定。
代码

// LeetCode, Search in Rotated Sorted Array
// 时间复杂度 O(log n)，空间复杂度 O(1)
class Solution {
    public static int search(int A[], int n, int target) {
       int first = 0, last = n;
       while (first != last) {
            int mid = (first + last) / 2;
            if (A[mid] == target)
                  return mid;
           if (A[first] <= A[mid]) {
                 if (A[first] <= target && target < A[mid])
                            last = mid;
                  else
                             first = mid + 1;
           } else {
                  if (A[mid] < target && target <= A[last-1])
                             first = mid + 1;
                  else
                              last = mid;
            }
         }
             return -1;
   }
}