搜索旋转排序数组

33. 搜索旋转排序数组

整数数组 nums 按升序排列，数组中的值 互不相同 。

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

#include <iostream>
#include <unordered_map>
#include <vector>
#include <algorithm>
using namespace std;

class Solution {
public:
    int search(vector<int> &nums, int target) {
        int left = 0;
        int right = nums.size() - 1;
        for (; left <= right;) {
            int mid = left + (right - left) / 2;
            if (nums[mid] == target) {
                return mid;
            } else if (nums[left] <= nums[mid]) {
                // 左侧是有序
                if (target >= nums[left] && target < nums[mid]) {
                    // 目标值在左侧
                    right = mid - 1;
                } else {
                    // 目标值在右侧
                    left = mid + 1;
                }
            } else {
                // 右侧是有序
                if (target > nums[mid] && target <= nums[right]) {
                    // 目标在右侧
                    left = mid + 1;
                } else {
                    // 目标在左侧
                    right = mid - 1;
                }
            }
        }
        return -1;
    }
};

int main()
{
    Solution *test = new Solution();
    vector<int> vec = {266, 267, 268, 269, 271, 278, 282, 292, 293, 298,
                       6, 9, 15, 19, 21, 26, 33, 35, 37, 38, 
                       39, 46, 49, 54, 65, 71, 74, 77, 79, 82,
                       83, 88, 92, 93, 94, 97, 104, 108, 114, 115,
                       117, 122, 123, 127, 128, 129, 134, 137, 141, 142,
                       144, 147, 150, 154, 160, 163, 166, 169, 172, 173,
                       177, 180, 183, 184, 188, 198, 203, 208, 210, 214,
                       218, 220, 223, 224, 233, 236, 241, 243, 253, 256,
                       257, 262, 263};
    int target = 208;
    std::cout << test->search(vec, target) << endl; // 67

    vec = {4, 5, 6, 7, 0, 1, 2};
    target = 0;
    std::cout << test->search(vec, target) << endl; // 4

    target = 4;
    std::cout << test->search(vec, target) << endl; // 0

    target = 2;
    std::cout << test->search(vec, target) << endl; // 6

    target = 9;
    std::cout << test->search(vec, target) << endl; // -1

    system("pause");
    return 0;
}

 

运行结果：