某个小镇有 N 个村庄,村庄编号1-N,给出 M 条单向道路,不存在环,即不存在 村庄A可以到达村庄B 且 村庄B也可以到达村庄A的情况.如果村庄A与村庄B之间存在一条单向道路,则说村庄A和村庄B之间存在联系,联系具有无向性,即如果村庄A和村庄B有联系,则村庄B和村庄A有联系:联系具有传递性,即如果存在村庄A和村庄B有联系,村庄B和村庄C有联系,则村庄A和村庄C有联系.现在小镇要在某些村庄里建垃圾站,对建垃圾站的村庄要满足与之有联系的村庄都可以通过单向道路到达该村庄.问小镇能建多少个垃圾站.  …

<剑指offer>解题笔记 <剑指offer>共50题,这两周使用C++花时间做了一遍,谨在此把一些非常巧妙的方法.写代码遇到的难点.易犯错的细节等做一个简单的标注,但不会太过具体.具体算法还是请參考书本. 做的比較急,代码还有非常多不完好的地方,如有错误.欢迎改正,地址为:github:sword_of_offer. 能够使用git clone https://github.com/heLomaN/sword_of_offer.git命令获代替码. 当中,少数无法验证正确与否的题…

122. Best Time to Buy and Sell Stock II 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 as many transactions as you like (ie, buy one and sell on…

110.Balanced Binary Tree Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. 很早以前做的了  准…

Find the length of the longest substring T of a given string (consists of lowercase letters only) such that every character in T appears no less than k times. Example 1: Input: s = "aaabb", k = 3 Output: 3 The longest substring is "aaa"…

Given a string, find the length of the longest substring without repeating characters. Examples: Given "abcabcbb", the answer is "abc", which the length is 3. Given "bbbbb", the answer is "b", with the length of 1.…

2. Add Two Numbers You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. You may ass…

Alex has invented a new game for fun. There are n integers at a board and he performs the following moves repeatedly: 1. He chooses three numbers a, b and c written at the board and erases them.2. He chooses two numbers from the triple a, b and c and…

1.简单的登陆题 解题链接: http://ctf5.shiyanbar.com/web/jiandan/index.php  Burp抓包解密 乱码,更换思路.尝试id intruder 似乎也没什么敏感内容,除了显示一个sql inject detected!啥的 扫一下目录吧 得到源代码 得到rootzz flag:{c42b2b758a5a36228156d9d671c37f19}…

卡拉兹(Callatz)猜想: 对任何一个正整数 n,如果它是偶数,那么把它砍掉一半:如果它是奇数,那么把 (3n+1) 砍掉一半.这样一直反复砍下去,最后一定在某一步得到 n=1.卡拉兹在 1950 年的世界数学家大会上公布了这个猜想,传说当时耶鲁大学师生齐动员,拼命想证明这个貌似很傻很天真的命题,结果闹得学生们无心学业,一心只证 (3n+1),以至于有人说这是一个阴谋,卡拉兹是在蓄意延缓美国数学界教学与科研的进展-- 我们今天的题目不是证明卡拉兹猜想,而是对给定的任一不超过 1000 的正整…