There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direct friend of C, then A is an indirect friend of C. And we defined a fri…

原题链接在这里:https://leetcode.com/problems/friend-circles/description/ 题目: There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direc…

Leetcode之深度优先搜索(DFS)专题-547. 朋友圈(Friend Circles) 深度优先搜索的解题详细介绍,点击 班上有 N 名学生.其中有些人是朋友,有些则不是.他们的友谊具有是传递性.如果已知 A 是 B 的朋友,B 是 C 的朋友,那么我们可以认为 A 也是 C 的朋友.所谓的朋友圈,是指所有朋友的集合. 给定一个 N * N 的矩阵 M,表示班级中学生之间的朋友关系.如果M[i][j] = 1,表示已知第 i 个和 j 个学生互为朋友关系,否则为不知道.你必须输出所有学生…

There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direct friend of C, then A is an indirect friend of C. And we defined a fri…

题目: https://leetcode.com/problems/friend-circles/ There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direct friend of C, then…

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 日期 题目地址:https://leetcode.com/problems/friend-circles/#/description 题目描述 There are N students in a class. Some of them are friends, while some are not. Their friendship is trans…

[题目链接]:https://leetcode.com/contest/leetcode-weekly-contest-26/problems/friend-circles/ [题意] 告诉你任意两个人是不是朋友. 问你最后有多少个连通块; [题解] 裸并查集. [完整代码] #include <bits/stdc++.h> using namespace std; #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 #d…

/* 思路就是遍历所有人,对于每一个人,寻找他的好友,找到好友后再找这个好友的好友 ,这样深度优先遍历下去,设置一个flag记录是否已经遍历了这个人. 其实dfs真正有用的是flag这个变量,因为如果m个人最多m个朋友圈,设置后flag后,相同的朋友圈会 检测到flag就会不算数. */ public int findCircleNum(int[][] M) { int m = M.length; if (m==0) return 0; int res = 0; boolean[] flag =…

A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positions to operate, count the number of islands after each addLand o…

463. Island Perimeterhttps://leetcode.com/problems/island-perimeter/就是逐一遍历所有的cell,用分离的cell总的的边数减去重叠的边的数目即可.在查找重叠的边的数目的时候有一点小技巧,就是沿着其中两个方向就好,这种题目都有类似的规律,就是可以沿着上三角或者下三角形的方向来做.一刷一次ac,但是还没开始注意codestyle的问题,需要再刷一遍. class Solution { public: int islandPerime…

In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all other nodes are descendants of this node, plus every node has exactly one parent, except for the root node which has no parents. The give…

Given two sentences words1, words2 (each represented as an array of strings), and a list of similar word pairs pairs, determine if two sentences are similar. For example, words1 = ["great", "acting", "skills"] and words2 = [&…

Given two sentences words1, words2 (each represented as an array of strings), and a list of similar word pairs pairs, determine if two sentences are similar. For example, "great acting skills" and "fine drama talent" are similar, if th…

Given a list accounts, each element accounts[i] is a list of strings, where the first element accounts[i][0] is a name, and the rest of the elements are emails representing emails of the account. Now, we would like to merge these accounts. Two accoun…

In this problem, a tree is an undirected graph that is connected and has no cycles. The given input is a graph that started as a tree with N nodes (with distinct values 1, 2, ..., N), with one additional edge added. The added edge has two different v…

请点击页面左上角 -> Fork me on Github 或直接访问本项目Github地址:LeetCode Solution by Swift    说明:题目中含有$符号则为付费题目. 如:[Swift]LeetCode156.二叉树的上下颠倒 $ Binary Tree Upside Down 请下拉滚动条查看最新 Weekly Contest!!! Swift LeetCode 目录 | Catalog 序        号 题名Title 难度     Difficulty  两数之…

Union Find算法基础 Union Find算法用于处理集合的合并和查询问题,其定义了两个用于并查集的操作: Find: 确定元素属于哪一个子集,或判断两个元素是否属于同一子集 Union: 将两个子集合并为一个子集 并查集是一种树形的数据结构,其可用数组或unordered_map表示: Find操作即查找元素的root,当两元素root相同时判定他们属于同一个子集:Union操作即通过修改元素的root(或修改parent)合并子集,下面两个图展示了id[6]由6修改为9的变化:   …

There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a directfriend of B, and B is a direct friend of C, then A is an indirect friend of C. And we defined a frie…

We have a grid of 1s and 0s; the 1s in a cell represent bricks.  A brick will not drop if and only if it is directly connected to the top of the grid, or at least one of its (4-way) adjacent bricks will not drop. We will do some erasures sequentially…

突然很想刷刷题,LeetCode是一个不错的选择,忽略了输入输出,更好的突出了算法,省去了不少时间. dalao们发现了任何错误,或是代码无法通过,或是有更好的解法,或是有任何疑问和建议的话,可以在对应的随笔下面评论区留言,我会及时处理,在此谢过了. 过程或许会很漫长,也很痛苦,慢慢来吧. 编号 题名 过题率 难度 1 Two Sum 0.376 Easy 2 Add Two Numbers 0.285 Medium 3 Longest Substring Without Repeating C…

算法思想 二分查找 贪心思想 双指针 排序 快速选择 堆排序 桶排序 搜索 BFS DFS Backtracking 分治 动态规划 分割整数 矩阵路径 斐波那契数列 最长递增子序列 最长公共子系列 0-1 背包 数组区间 字符串编辑 其它问题 数学 素数 最大公约数 进制转换 阶乘 字符串加法减法 相遇问题 多数投票问题 其它 数据结构相关 栈和队列 哈希表 字符串 数组与矩阵 1-n 分布 有序矩阵 链表 树 递归 层次遍历 前中后序遍历 BST Trie 图 位运算 参考资料 算法思想 二…

LeetCode高频题目(100)汇总-Java实现       LeetCode高频题目(100)汇总-Java实现 目录 第01-50题 [Leetcode-easy-1] Two Sum [Leetcode-easy-2] Add Two Numbers [Leetcode-easy-3] Longest Substring Without Repeating Characters [Leetcode-easy-5] Longest Palindromic Substring [Leetc…

写的有点晚了. 我每次都是先看一下这里http://bookshadow.com/leetcode/的思路,然后再开始写我自己的. 1. 521. Longest Uncommon Subsequence I 说实话,看完就懵逼了,这怎么做,难道是dp,后仔细一想,不对啊,很简单啊. 只要2个字符串不相等,返回长度较长的那个就行了. 刚开始,考虑,如果其中之一为空串,我返回的-1,不知道怎么想的.这显然是错的. class Solution { public: int findLUSlength…

Two strings X and Y are similar if we can swap two letters (in different positions) of X, so that it equals Y. For example, "tars" and "rats" are similar (swapping at positions 0 and 2), and "rats" and "arts" are si…

Given two sentences words1, words2 (each represented as an array of strings), and a list of similar word pairs pairs, determine if two sentences are similar. For example, words1 = ["great", "acting", "skills"] and words2 = [&…

Given a list accounts, each element accounts[i] is a list of strings, where the first element accounts[i][0] is a name, and the rest of the elements are emails representing emails of the account. Now, we would like to merge these accounts. Two accoun…

In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all other nodes are descendants of this node, plus every node has exactly one parent, except for the root node which has no parents. The give…

In this problem, a tree is an undirected graph that is connected and has no cycles. The given input is a graph that started as a tree with N nodes (with distinct values 1, 2, ..., N), with one additional edge added. The added edge has two different v…

A 2d grid map of m rows and n columns is initially filled with water. We may perform an addLand operation which turns the water at position (row, col) into a land. Given a list of positions to operate, count the number of islands after each addLand o…

All LeetCode Questions List(Part of Answers, still updating) 题目汇总及部分答案(持续更新中) Leetcode problems classified by company 题目按公司分类(Last updated: October 2, 2017) .   Top Interview Questions # Title Difficulty Acceptance 1 Two Sum Medium 17.70% 2 Add Two N…