时间轴

2025-12-04

init

题目：

P33 搜索旋转排序数组

https://leetcode.cn/problems/search-in-rotated-sorted-array/description/?envType=study-plan-v2&envId=top-interview-150

二分本质是排除掉另一半：

  • 如果左半边是递增的且target不处于这个区间，那么target必定在右半边
  • 如果右半边是递增的且target不处于这个区间，那么target必定在左半边
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#include <vector>
using std::vector;

class Solution {
    public:
        int search(vector<int> &nums, int target)
        {
                int n = nums.size();
                int left = 0, right = n - 1;
                int mid;
                while (left <= right) {
                        mid = left + (right - left) / 2;

                        if (nums[mid] == target) {
                                return mid;
                        }

                        if (nums[left] <= nums[mid]) {
                                if (nums[left] <= target &&
                                    target < nums[mid]) {
                                        right = mid - 1;
                                } else {
                                        left = mid + 1;
                                }
                        }else if (nums[right] >= nums[mid]) {
                                if (nums[mid] < target &&
                                    target <= nums[right]) {
                                        left = mid + 1;
                                } else {
                                        right = mid - 1;
                                }
                        }
                }
                return -1;
        }
};