搜索旋转排序数组

33. 搜索旋转排序数组

在传递给函数之前，nums 在预先未知的某个下标 k（0 <= k < nums.length）上进行了 旋转，使数组变为 [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]]（下标 从 0 开始 计数）。例如， [0,1,2,4,5,6,7] 在下标 3 处经旋转后可能变为 [4,5,6,7,0,1,2] 。

给你 旋转后 的数组 nums 和一个整数 target ，如果 nums 中存在这个目标值 target ，则返回它的下标，否则返回 -1 。

示例 1：

输入：nums = [4,5,6,7,0,1,2], target = 0
输出：4

示例 2：

输入：nums = [4,5,6,7,0,1,2], target = 3
输出：-1

示例 3：

输入：nums = [1], target = 0
输出：-1

提示：

• 1 <= nums.length <= 5000
• -10^4 <= nums[i] <= 10^4
• nums 中的每个值都 独一无二
• 题目数据保证 nums 在预先未知的某个下标上进行了旋转
• -10^4 <= target <= 10^4

 1 #include 
 2 #include 
 3 #include 
 4 #include 
 5 using namespace std;
 6 
 7 class Solution {
 8 public:
 9     int search(vector<int> &nums, int target) {
10         int left = 0;
11         int right = nums.size() - 1;
12         for (; left <= right;) {
13             int mid = left + (right - left) / 2;
14             if (nums[mid] == target) {
15                 return mid;
16             } else if (nums[left] <= nums[mid]) {
17                 // 左侧是有序
18                 if (target >= nums[left] && target < nums[mid]) {
19                     // 目标值在左侧
20                     right = mid - 1;
21                 } else {
22                     // 目标值在右侧
23                     left = mid + 1;
24                 }
25             } else {
26                 // 右侧是有序
27                 if (target > nums[mid] && target <= nums[right]) {
28                     // 目标在右侧
29                     left = mid + 1;
30                 } else {
31                     // 目标在左侧
32                     right = mid - 1;
33                 }
34             }
35         }
36         return -1;
37     }
38 };
39 
40 int main()
41 {
42     Solution *test = new Solution();
43     vector<int> vec = {266, 267, 268, 269, 271, 278, 282, 292, 293, 298,
44                        6, 9, 15, 19, 21, 26, 33, 35, 37, 38, 
45                        39, 46, 49, 54, 65, 71, 74, 77, 79, 82,
46                        83, 88, 92, 93, 94, 97, 104, 108, 114, 115,
47                        117, 122, 123, 127, 128, 129, 134, 137, 141, 142,
48                        144, 147, 150, 154, 160, 163, 166, 169, 172, 173,
49                        177, 180, 183, 184, 188, 198, 203, 208, 210, 214,
50                        218, 220, 223, 224, 233, 236, 241, 243, 253, 256,
51                        257, 262, 263};
52     int target = 208;
53     std::cout << test->search(vec, target) << endl; // 67
54 
55     vec = {4, 5, 6, 7, 0, 1, 2};
56     target = 0;
57     std::cout << test->search(vec, target) << endl; // 4
58 
59     target = 4;
60     std::cout << test->search(vec, target) << endl; // 0
61 
62     target = 2;
63     std::cout << test->search(vec, target) << endl; // 6
64 
65     target = 9;
66     std::cout << test->search(vec, target) << endl; // -1
67 
68     system("pause");
69     return 0;
70 }

运行结果：