传送门 一道做了巨久,不过确实很好的题 发现不定边权极难处理,所以就不会 感觉和这题有点像,但还是不会 但发现题面里有个地方很套路 要求有哪些点/边最终可以满足最短/最小,比如这样或这样的题,考虑凸包,最终在凸包上的点就是能取到最值的点 所以考虑如何维护凸包 根据题解,发现为了确定一条路径的权值,我们需要知道这条路上经过了多少条-1边 所以需要处理出经过 \(k\) 条-1边时到终点的最短路 发现这个东西很难实现,考虑二维spfa 当题目要求「在某种特定访问顺序(先去过红点才能去蓝点/必须按一红…

题目来源: https://leetcode.com/problems/clone-graph/ 题意分析: 克隆一个无向图.每个节点包括一个数值和它的邻居. 题目思路: 直接深度拷贝. 代码(python): # Definition for a undirected graph node # class UndirectedGraphNode(object): # def __init__(self, x): # self.label = x # self.neighbors = [] cl…

Sasha and Interesting Fact from Graph Theory n 个 点形成 m 个有标号森林的方案数为 F(n, m) = m * n ^ {n - 1 - m} 然后就没啥难度了... #include<bits/stdc++.h> #define LL long long #define LD long double #define ull unsigned long long #define fi first #define se second #defin…

Problem Description Wang Haiyang is a strong and optimistic Chinese youngster. Although born and brought up in the northern inland city Harbin, he has deep love and yearns for the boundless oceans. After graduation, he came to a coastal city and got…

Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finite set, its elements being called vertices (or nodes). Let E be a subset of the Cartesian product V×V, its elements being called edges. Then G…

Connected Graph Time Limit: 1000MS   Memory Limit: 30000K Total Submissions: 3156   Accepted: 1533 Description An undirected graph is a set V of vertices and a set of E∈{V*V} edges.An undirected graph is connected if and only if for every pair (u,v)…

这道题我第一次的想法是直接判环的数量,然而事实证明实在是太naive了. 随便画个图都可以卡掉我的解法.(不知道在想什么) 这道题的正解是拓扑排序. 朴素的想法是对所有边都跑一次拓扑,但这样$O(m(n+m))$会炸,于是可以有下面的优化. 我们找到所有入度不为零的点,然后把他们每一个都删掉一条边跑一遍拓扑排序. 那么这样就可以优化到$O(n(n+m))$了,稳得一批. AC代码如下: 1935ms 1356kb #include<bits/stdc++.h> using namespace…

Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finite set, its elements being called vertices (or nodes). Let E be a subset of the Cartesian product V×V, its elements being called edges. Then G…

题目链接G题 题意 序列 \(a_1,a_2,⋯,a_n\) 是一个排列, 当且仅当它含有 1 到 n 的所有整数. 排列 \(a_1,a_2,⋯,a_n\) 是一个有向图的拓扑排序,当且仅当对于每条边 \(u→v\),这个排列中 \(u\) 都出现在 \(v\) 之前. 给定一个有向无环图,添加至多 k 条有向边,使图保持无环,且字典序最小的拓扑排序字典序最大 思路 很有意思的一道构造题. 主要想法就是字典序较大的连边限制字典序小的. 两个堆:一个小根一个大根(小根堆是当前可以填写的节点集合,…

本题分两步: 1 使用Tarjan算法求全部最大子强连通图.而且标志出来 2 然后遍历这些节点看是否有出射的边,没有的顶点所在的子强连通图的全部点,都是解集. Tarjan算法就是模板算法了. 这里使用一个数组和一个标识号,就能够记录这个顶点是属于哪个子强连通图的了. 然后使用DFS递归搜索全部点及其边,假设有边的还有一个顶点不属于本子强连通图.那么就说明有出射的边. 有难度的题目: #include <stdio.h> #include <stdlib.h> #include &…

1.题目描述 2.问题分析 要遍历图,然后标记没有被复制的节点. 3.代码 class Solution { private: unordered_map<Node*, Node*> m; public: Node* cloneGraph(Node* node) { if (node == NULL) return NULL; Node *copy = new Node(node->val, {}); queue<Node*> q; m[node] = copy; q.pus…

题意:给你n个点,m条无向边,每个点都属于一个层,相邻层的任意点都能花费C到另一层任意点,问你1到n最小路径 思路:没理解题意,以为每一层一个点,题目给的是第i个点的层数编号.这道题的难点在于建边,如果用最朴素的相邻层所有点互相连接,那么可能有5*10^4连5*10^4,复杂度O(n^2).这里我们用拆点(?大概),把每一层拆出一个点,作为每一层点和相邻层连接的中转站.这里要特别注意,同一层的点的距离不是0,所以我们建边不能全是无向边: 1.层与层无向边,权值C 2.层与同层点建单向边,权值0…

\[ \text{Preface} \] 算是一道思维难度稍易,代码难度稍难的题吧. \[ \text{Description} \] 给出一张 \(n\) 个点,\(m\) 条边的图,点带权.需要支持三个操作: D x 删掉编号为 \(x\) 的边 Q x k 查询与节点 \(x\) 联通的所有节点中,点权第 \(k\) 大节点的点权 C x v 将节点 \(x\) 点权改为 \(v\) 多组数据,每组数据最终需要输出所有查询的平均值 ( 保留 6 位 ) ,没有强制在线. \[ \text{…

思路:将黑边标记为1,白边标记为100000,树链剖分 如果查询时ans超过100000,那就有白边,输出-1,不然直接输出ans #include<bits/stdc++.h> #define maxn 800001 #define int long long #define L(x) (x<<1) #define R(x) ((x<<1)|1) using namespace std; int tree[maxn],tag[maxn]; int rev[maxn],…

Content \(\textsf{CQXYM}\) 想要构造一个包含 \(n\) 个点和 \(m\) 条边的无向连通图,并且他希望这个图满足下列条件: 该图中不存在重边和自环.也就是说,一条边应该连接两个不同的顶点,且两个点之间最多只能连一条边. 该图的直径严格小于 \(k-1\). 定义: 一个图中两个节点之间的距离是以这两个点为端点的路径经过的最小边数. 一个图的直径是任意两点之间距离的最大值. \(\textsf{CQXYM}\) 想知道他能不能够造出这样一个图.由于他还忙于其他事情,于…

Destroying The Graph Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 8198   Accepted: 2635   Special Judge Description Alice and Bob play the following game. First, Alice draws some directed graph with N vertices and M arcs. After that B…

题目: Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors. OJ's undirected graph serialization: Nodes are labeled uniquely. We use # as a separator for each node, and , as a separator for node label and each n…

又是虚脱的一天啊QAQ,早上习惯性迟到,九点多到学校开始码题,六道题看下来花了将近一个小时,主要纠结于第二题和第六题.到了十点,没再深入思考,开始码题.. 一直到十一点半,写了两道题.然后吃完饭后中午把剩下会的两道题水了水就开始去主攻第六题,第二题感觉不是很有思路. 然后就从三点想到四点,中间考量了很多算法好像都不行,但我能确定这是一道最短路的计数问题,相关的题目之前做过一道,但是面对这道题还不是很有想法.无奈,最后码了暴力走人. 今天没精力再改题了,一会还要补文化课的作业,具体的题解和小结什么…

Codeforces Round #261 (Div. 2) E - Pashmak and Graph E. Pashmak and Graph time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Pashmak's homework is a problem about graphs. Although he always tr…

Sparse Graph Problem Description   In graph theory, the complement of a graph G is a graph H on the same vertices such that two distinct vertices of H are adjacent if and only if they are notadjacent in G. Now you are given an undirected graph G of N…

原题链接在这里:https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/ 题目: Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected com…

Connected Graph Time Limit: 1000MS   Memory Limit: 30000K Total Submissions: 3156   Accepted: 1533 Description An undirected graph is a set V of vertices and a set of E∈{V*V} edges.An undirected graph is connected if and only if for every pair (u,v)…

[UOJ#12][UER #1]猜数 试题描述 这一天,小Y.小D.小C正在愉快地玩耍. 小Y是个数学家,他一拍脑袋冒出了一个神奇的完全平方数 n. 小D是个机灵鬼,很快从小Y嘴里套出了 n的值.然后在脑内把 n写成了 a×b的形式.其中 a,b 都是正整数. 小C是个八卦狂,他发现小D从小Y那里获知了神奇的东西,于是死缠烂打追问小D.最后小D说道:“我可以告诉你正整数 g和 l的值,我保证 ab=gl=n且 a,b都是 g 的倍数.但是 a,b 我可不能告诉你.” 这可急坏了小C.他决定退而求…

博客搬至blog.csgrandeur.com,cnblogs不再更新. 新的题解会更新在新博客:http://blog.csgrandeur.com/2014/01/15/LeetCode-OJ-Solution/ ———————————————————————————————————————— ———————————————————————————————————————— LeetCode OJ 题解 LeetCode OJ is a platform for preparing tech…

C. Graph and String 题目连接: http://codeforces.com/contest/624/problem/C Description One day student Vasya was sitting on a lecture and mentioned a string s1s2... sn, consisting of letters "a", "b" and "c" that was written on hi…

题目链接: 题目 Graph Construction Time limit: 3.000 seconds 问题描述 Graph is a collection of edges E and vertices V. Graph has a wide variety of applications in computer. There are different ways to represent graph in computer. It can be represented by adjace…

网络流/二分图最小点权覆盖 果然还是应该先看下胡伯涛的论文…… orz proverbs 题意: N个点M条边的有向图,给出如下两种操作.删除点i的所有出边,代价是Ai.删除点j的所有入边,代价是Bj.求最后删除图中所有的边的最小代价. 其实就是二分图最小点权覆盖. 定义:从x或者y集合中选取一些点,使这些点覆盖所有的边,并且选出来的点的权值尽可能小. 题解: 拆点.n个点拆成2n个点(左右各n个,i与(i+n)对应,之间连容量INF的边),S和i连容量为Ai的边,(i+n)与T之间连容量为Bi…

D. Mr. Kitayuta's Colorful Graph Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/506/problem/D Description Mr. Kitayuta has just bought an undirected graph with n vertices and m edges. The vertices of the graph are numbered…

C. Graph Reconstruction Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/329/problem/C Description I have an undirected graph consisting of n nodes, numbered 1 through n. Each node has at most two incident edges. For each pa…

题目地址:http://poj.org/problem?id=2553 The Bottom of a Graph Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 7881   Accepted: 3263 Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finit…