【leetcode】Container With Most Water（middle）

Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a containe…

【leetcode】Search for a Range（middle）

Given a sorted array of integers, find the starting and ending position of a given target value. Your algorithm's runtime complexity must be in the order of O(log n). If the target is not found in the array, return [-1, -1]. For example,Given [5, 7,…

【leetcode】Swap Nodes in Pairs （middle）

Given a linked list, swap every two adjacent nodes and return its head. For example,Given 1->2->3->4, you should return the list as 2->1->4->3. Your algorithm should use only constant space. You may not modify the values in the list, onl…

【leetcode】Linked List Cycle II （middle）

Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Follow up:Can you solve it without using extra space? 思路: 做过,就当复习了. 先用快慢指针判断相交,关键是环开始点的获取. 用上图说明一下,设非环的部分长度为a(包括环的入口点), 环的长度为b(包括环的入口点). 快慢指针相交的位置为绿色的点,距离…

【leetcode】Reverse Linked List II （middle）

Reverse a linked list from position m to n. Do it in-place and in one-pass. For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4, return 1->4->3->2->5->NULL. 思路: 好困啊,脑子晕晕的. 转了半天AC了.但写的很罗嗦,要学习大神的写法. 注意翻转的写法. 用伪头部大神14行简洁代码 L…

【leetcode】Path Sum I & II（middle）

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ \ 7 2 1 return true…

【leetcode】Binary Search Tree Iterator（middle）

Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST. Calling next() will return the next smallest number in the BST. Note: next() and hasNext() should run in average O(1) time and uses…

【leetcode】Validate Binary Search Tree（middle）

Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node contains only nodes with keys…

【leetcode】Minimum Size Subarray Sum（middle）

Given an array of n positive integers and a positive integer s, find the minimal length of a subarray of which the sum ≥ s. If there isn't one, return 0 instead. For example, given the array [2,3,1,2,4,3] and s = 7,the subarray [4,3] has the minimal…

【leetcode】Evaluate Reverse Polish Notation（middle）

Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some examples: ["2", "1", "+", "3", "*"] -&g…

【LeetCode】120. Triangle 解题报告（Python）

[LeetCode]120. Triangle 解题报告(Python) 作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 题目地址https://leetcode.com/problems/triangle/description/ 题目描述: Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjac…

【LeetCode】10.Regular Expression Matching（dp）

[题意] 给两个字符串s和p,判断s是否能用p进行匹配. [题解] dp[i][j]表示s的前i个是否能被p的前j个匹配. 首先可以分成3大类情况,我们先从简单的看起: (1)s[i - 1] = p[j - 1],易得dp[i][j] = dp[i-1][j-1] (2)p[i - 1] = '.',因为'.'可以匹配任何字符,所以dp[i][j] = dp[i-1][j-1] (3)p[i - 1] = '*',这种情况就比较复杂了. 当p[j - 2] != s[i - 1] &&…

【leetcode】Container With Most Water

题目描述: Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a co…

【LeetCode】51. N-Queens 解题报告（C++）

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回溯法日期题目地址:https://leetcode.com/problems/n-queens/ 题目描述 The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.…

【LeetCode】274. H-Index 解题报告（Python）

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 题目地址: https://leetcode.com/problems/h-index/description/ 题目描述: Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's…

【LeetCode】389 Find the Difference（java）

原题 Given two strings s and t which consist of only lowercase letters. String t is generated by random shuffling string s and then add one more letter at a random position. Find the letter that was added in t. Example: Input: s = "abcd" t = "…

【leetcode】Reverse Nodes in k-Group （hard）☆

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is. You may not alter the values in the nodes, only nod…

【leetcode】Merge Two Sorted Lists（easy）

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. 思路:使用伪头部 class Solution { public: ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) { ListNode fakehead();…

【leetcode】Remove Linked List Elements（easy）

Remove all elements from a linked list of integers that have value val. ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5 思路:简单题. //Definition for singly-linked list. struct ListNod…

【leetcode】Contains Duplicate & Rectangle Area（easy）

Contains Duplicate Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct. 思路:简单题用set bool cont…

【leetcode】917. Reverse Only Letters（双指针）

Given a string s, reverse the string according to the following rules: All the characters that are not English letters remain in the same position. All the English letters (lowercase or uppercase) should be reversed. class Solution { public: string r…

【LeetCode】9、Palindrome Number（回文数）

题目等级:Easy 题目描述: Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward. Example 1: Input: 121 Output: true Example 2: Input: -121 Output: false Explanation: From left to right, it reads -12…

【原】FMDB源码阅读（三）

[原]FMDB源码阅读(三) 本文转载请注明出处 —— polobymulberry-博客园 1. 前言 FMDB比较优秀的地方就在于对多线程的处理.所以这一篇主要是研究FMDB的多线程处理的实现.而FMDB最新的版本中主要是通过使用FMDatabaseQueue这个类来进行多线程处理的. 2. FMDatabaseQueue使用举例 // 创建,最好放在一个单例的类中 FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath…

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