Day26力扣打卡

Day26力扣打卡

打卡记录

搜索旋转排序数组（二分）

链接

class Solution {int findMin(vector<int> &nums) {int left = -1, right = nums.size() - 1; // 开区间 (-1, n-1)while (left + 1 < right) { // 开区间不为空int mid = left + (right - left) / 2;if (nums[mid] < nums.back()) right = mid; // 蓝色else left = mid; // 红色}return right;}int lower_bound(vector<int> &nums, int left, int right, int target) {int r0 = right;while (left + 1 < right) { // 开区间不为空// 循环不变量：// nums[left] < target// nums[right] >= targetint mid = left + (right - left) / 2;if (nums[mid] < target)left = mid; // 范围缩小到 (mid, right)elseright = mid; // 范围缩小到 (left, mid)}return right < r0 && nums[right] == target ? right : -1;}public:int search(vector<int> &nums, int target) {int i = findMin(nums), left, right;if (target > nums.back()) left = -1, right = i; // 左段else left = i - 1, right = nums.size(); // 右段return lower_bound(nums, left, right, target);}
};