786. 第 K 个最小的素数分数 一个已排序好的表 A,其包含 1 和其他一些素数. 当列表中的每一个 p<q 时,我们可以构造一个分数 p/q . 那么第 k 个最小的分数是多少呢? 以整数数组的形式返回你的答案, 这里 answer[0] = p 且 answer[1] = q. 示例: 输入: A = [1, 2, 3, 5], K = 3 输出: [2, 5] 解释: 已构造好的分数,排序后如下所示: 1/5, 1/3, 2/5, 1/2, 3/5, 2/3. 很明显第三个最小的分数是…

A sorted list A contains 1, plus some number of primes.  Then, for every p < q in the list, we consider the fraction p/q. What is the K-th smallest fraction considered?  Return your answer as an array of ints, where answer[0] = p and answer[1] = q. E…

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 解题思路一: 之前我们有mergeTwoLists(ListNode l1, ListNode l2)方法,直接调用的话,需要k-1次调用,每次调用都需要产生一个ListNode[],空间开销很大.如果采用分治的思想,对相邻的两个ListNode进行mergeTwoLists,每次将规模减少一半,直到…

798. 得分最高的最小轮调 给定一个数组 A,我们可以将它按一个非负整数 K 进行轮调,这样可以使数组变为 A[K], A[K+1], A{K+2], - A[A.length - 1], A[0], A[1], -, A[K-1] 的形式.此后,任何值小于或等于其索引的项都可以记作一分. 例如,如果数组为 [2, 4, 1, 3, 0],我们按 K = 2 进行轮调后,它将变成 [1, 3, 0, 2, 4].这将记作 3 分,因为 1 > 0 [no points], 3 > 1 [no…

692. 前K个高频单词 给一非空的单词列表,返回前 k 个出现次数最多的单词. 返回的答案应该按单词出现频率由高到低排序.如果不同的单词有相同出现频率,按字母顺序排序. 示例 1: 输入: ["i", "love", "leetcode", "i", "love", "coding"], k = 2 输出: ["i", "love"] 解析: &…

658. 找到 K 个最接近的元素 给定一个排序好的数组,两个整数 k 和 x,从数组中找到最靠近 x(两数之差最小)的 k 个数.返回的结果必须要是按升序排好的.如果有两个数与 x 的差值一样,优先选择数值较小的那个数. 示例 1: 输入: [1,2,3,4,5], k=4, x=3 输出: [1,2,3,4] 示例 2: 输入: [1,2,3,4,5], k=4, x=-1 输出: [1,2,3,4] 说明: k 的值为正数,且总是小于给定排序数组的长度. 数组不为空,且长度不超过 104…

23. 合并K个排序链表 合并 k 个排序链表,返回合并后的排序链表.请分析和描述算法的复杂度. 示例: 输入: [ 1->4->5, 1->3->4, 2->6 ] 输出: 1->1->2->3->4->4->5->6 来源:力扣(LeetCode) 链接:https://leetcode-cn.com/problems/merge-k-sorted-lists 著作权归领扣网络所有.商业转载请联系官方授权,非商业转载请注明出处.…

779. 第K个语法符号 在第一行我们写上一个 0.接下来的每一行,将前一行中的0替换为01,1替换为10. 给定行数 N 和序数 K,返回第 N 行中第 K个字符.(K从1开始) 例子: 输入: N = 1, K = 1 输出: 0 输入: N = 2, K = 1 输出: 0 输入: N = 2, K = 2 输出: 1 输入: N = 4, K = 5 输出: 1 解释: 第一行: 0 第二行: 01 第三行: 0110 第四行: 01101001 注意: N 的范围 [1, 30]. K…

347. 前 K 个高频元素 给定一个非空的整数数组,返回其中出现频率前 k 高的元素. 示例 1: 输入: nums = [1,1,1,2,2,3], k = 2 输出: [1,2] 示例 2: 输入: nums = [1], k = 1 输出: [1] 说明: 你可以假设给定的 k 总是合理的,且 1 ≤ k ≤ 数组中不相同的元素的个数. 你的算法的时间复杂度必须优于 O(n log n) , n 是数组的大小. class Solution { //前 K 个高频元素 public Li…

60. 第k个排列 给出集合 [1,2,3,-,n],其所有元素共有 n! 种排列. 按大小顺序列出所有排列情况,并一一标记,当 n = 3 时, 所有排列如下: "123" "132" "213" "231" "312" "321" 给定 n 和 k,返回第 k 个排列. 说明: 给定 n 的范围是 [1, 9]. 给定 k 的范围是[1, n!]. 示例 1: 输入: n = 3,…

Given a binary search tree, write a function kthSmallest to find the kth smallest element in it. Note: You may assume k is always valid, 1 ≤ k ≤ BST's total elements. 求二叉树中第k个最小的元素,中序遍历就可以了,具体代码和另一个Binary Tree Iterator差不多其实,这题由于把=写成了==调bug调了好久,细心细心啊啊…

现在有这么一道题目:要求从多个的数据中查找出前K个最小或最大值 分析:有多种方案可以实现.一.最容易想到的是先对数据快速排序,然后输出前k个数字.   二.先定义容量为k的数组,从源数据中取出前k个填充此数组,调整此数组的最大值maxValue到首位,然后对剩下的n-k个数据迭代,对于每个遍历到的数字x,如果x < maxValue,用x把maxValue替换掉,然后调整数组最大值的位置. 三.基于二的思路,维护容量为k的堆,从源数据中取出前k个填充实例化堆,调整此堆中的最大值maxValue到…

230. 二叉搜索树中第K小的元素 给定一个二叉搜索树,编写一个函数 kthSmallest 来查找其中第 k 个最小的元素. 说明: 你可以假设 k 总是有效的,1 ≤ k ≤ 二叉搜索树元素个数. 示例 1: 输入: root = [3,1,4,null,2], k = 1 3 / \ 1 4 \ 2 输出: 1 示例 2: 输入: root = [5,3,6,2,4,null,null,1], k = 3 5 / \ 3 6 / \ 2 4 / 1 输出: 3 进阶: 如果二叉搜索树经常被…

Given strings S and T, find the minimum (contiguous) substring W of S, so that T is a subsequenceof W. If there is no such window in S that covers all characters in T, return the empty string "". If there are multiple such minimum-length windows…

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Ensure that numbers within the set are sorted in ascending order. Example 1…

Given a 2D board and a list of words from the dictionary, find all words in the board. Each word must be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same le…

Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete at most k transactions. 解题思路: https://leetcode.com/discuss/18330/is-it-best-solution-with-o-n-o-1…

The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, We get the following sequence (ie, for n = 3): "123" "132" "213" "231" "312" "…

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge…

LeetCode:前K个高频单词[692] 题目描述 给一非空的单词列表,返回前 k 个出现次数最多的单词. 返回的答案应该按单词出现频率由高到低排序.如果不同的单词有相同出现频率,按字母顺序排序. 示例 1: 输入: ["i", "love", "leetcode", "i", "love", "coding"], k = 2 输出: ["i", "lov…

LeetCode:前K个高频元素[347] 题目描述 给定一个非空的整数数组,返回其中出现频率前 k 高的元素. 示例 1: 输入: nums = [1,1,1,2,2,3], k = 2 输出: [1,2] 示例 2: 输入: nums = [1], k = 1 输出: [1] 说明: 你可以假设给定的 k 总是合理的,且 1 ≤ k ≤ 数组中不相同的元素的个数. 你的算法的时间复杂度必须优于 O(n log n) , n 是数组的大小. 题目分析 我们还是基于优先队列或者说是小顶堆来AC这…

Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit. 解题思路…

Given n, generate all structurally unique BST's (binary search trees) that store values 1...n. For example, Given n = 3, your program should return all 5 unique BST's shown below. 解题思路: 参考Java for LeetCode 096 Unique Binary Search Trees思路,本题很容易解决.注意,…

Given a collection of integers that might contain duplicates, nums, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example, If nums = [1,2,2], a soluti…

For an integer n, we call k>=2 a good base of n, if all digits of n base k are 1. Now given a string representing n, you should return the smallest good base of n in string format. Example 1: Input: "13" Output: "3" Explanation: 13…

LeetCode:第K个排列[60] 题目描述 给出集合 [1,2,3,…,n],其所有元素共有 n! 种排列. 按大小顺序列出所有排列情况,并一一标记,当 n = 3 时, 所有排列如下: "123""132""213""231""312""321" 给定 n 和 k,返回第 k 个排列. 说明: 给定 n 的范围是 [1, 9].给定 k 的范围是[1,  n!]. 示例 1: 输入…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 小根堆 日期 题目地址:https://leetcode.com/problems/k-closest-points-to-origin/ 题目描述 We have a list of points on the plane. Find the K closest points to the origin (0, 0). (Here, the dis…

Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. For example: Given "aacecaaa", return "aaacecaaa&qu…

Design a data structure that supports the following two operations: void addWord(word)bool search(word) search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.…

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…