leetcode 33. 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.

[Solution]

1) A[middle] > A[left], 说明 A[left, middle]有序。

2) A[middle] < A[left], 说明 A[middle, right]有序。

 1 int search(int A[], int n, int target)
 2     {
 3         int left = 0, right = n - 1, middle;
 4
 5         while (left <= right)
 6         {
 7             middle = (left + right) >> 1;
 8             if (A[middle] == target)
 9                 return middle;
10             if (A[middle] > A[left])
11             {
12                 if (target >= A[left] && target < A[middle])
13                     right = middle - 1;
14                 else
15                     left = middle + 1;
16             }
17             else if (A[middle] < A[left])
18             {
19                 if (target > A[middle] && target <= A[right])
20                     left = middle + 1;
21                 else
22                     right = middle - 1;
23             }
24             else
25             {
26                 middle = right;
27                 break;
28             }
29         }
30
31         return A[middle] == target ? middle : -1;
32     }