http://codeforces.com/gym/101246/problem/G 题意: 给出一个有向图,现在可以把图中的任意一条边改为无向边,问强连通分量最多可以有多少个点,在此情况下输出所有能改的边. 思路: 先dfs求出每个点能到达的点,用一个二维数组来存一下. 接下来枚举每一条边,把 u-v 这条边改为无向边,那么如果存在一点k,满足u->k并且k->v或者v->k并且k->u,那么k肯定是在这个强连通分量当中的.这样就可以计算出修改每一条边时所对应的点的个数. #in…

给你一张有向图,问你将任意一条边变成双向后,所能得到的最大强连通分量的大小. 缩点之后,预处理can(i,j)表示i能到j. 之后枚举每一条边(u,v),再枚举其他所有点t,如果can(u,t) && can(t,v),则t能和u.v共在一个强连通分量,尝试更新答案. #include<cstdio> #include<algorithm> #include<vector> #include<cstring> using namespace…

原题链接:http://codeforces.com/gym/100338/attachments/download/2136/20062007-winter-petrozavodsk-camp-andrew-stankevich-contest-22-asc-22-en.pdf 题意 给你一个无向图,要从1走到n,问你哪些边去掉之后就没法走原本的最短路了. 题解 跑两发最短路,顺着跑一发,倒着跑一发,对于边(u,v),如果w(u,v)+d[u]+rd[v]或者w(u,v)+d[v]+rd[u]…

http://codeforces.com/gym/101246/problem/G 题意:有一个n个点m条边的有向图,现在可以修改某一条有向边使得其为无向边,问修改哪些边可以使得修改后的强连通分量的点数最多,输出. 思路: 要使得修改边后的强连通分量的点数最多,假设当前修改的边的入点为u,出点为v,那么能在修改当前的边之后在强连通分量里面的点i,当且仅当修改边之前u能到达i并且i能到达v,然后修改之后,i就能通过v回到u,这样就是强连通的了.比如上面这个样例的1->5这条边,1(u)能到达1.…

题意:一颗树,每条边有个颜色,一条路径被定义为“彩虹”,当且仅当其上没有长度大于等于2的同色子路径.一个结点被定义为“超级结点”,当且仅当从其发出的所有路径都是“彩虹”. 枚举所有长度为2,且同色的路径,其两端点方向发出的子树中的结点都不可能成为答案,只需要将它们覆盖掉即可,用dfs序处理,在左端点+1,右端点-1,最后求个前缀和,为0的结点就是没有被覆盖过的结点,也即“超级结点”. 分两种情况:这两条边深度相同:这两条边深度不同. #include<cstdio> #include<m…

题目传送门 题意: 给出一幅无向带权图,q次询问,每次询问都求一棵包含给出的边的最小生成树. 思路: 首先求出最小生成树(kruskal),如果查询的边在最小生成树上,肯定是直接输出最小生成树,如果不在树上,那么这条必须连的边会和生成树形成一个环,我们就要去掉这个环上最大的一条边,就得到了答案(最小生成树是通过局部最优解得到全局最优解的,所以如果这样做,得到的是符合要求的最优解). 赛中队友提出一个问题,如果有两棵不同的最小生成树那这个做法不就错了吗,但其实如果有两棵最小生成树,这两棵树 相同权…

正反两次最短路用于判断边是不是最短路上的边,把最短路径上的边取出来建图.然后求割边.注意重边,和卡spfa. 正权,好好的dijkstra不用,用什么spfa? #include<bits/stdc++.h> using namespace std; typedef long long ll; #define fi first #define se second #define bug(x) cout<<#x<<'='<<x<<endl; #de…

题意:给你一幅图,问有多少条路径使得去掉该条路后最短路发生变化. 思路:先起始两点求两遍单源最短路,利用s[u] + t[v] + G[u][v] = dis 找出所有最短路径,构造新图.在新图中找到所有的桥输出就可以了. #include <iostream> #include <cstdio> #include <fstream> #include <algorithm> #include <cmath> #include <deque…

要back的题目 目标是全绿!back一题删一题! acmm7 1003 1004 acmm8 1003 1004 sysu20181013 Stat Origin Title Solved A Gym 100624A Kingdoms   B Gym 100624B Who wants to live forever? Solved C Gym 100624C Chemist's vows   D Gym 100624D Non-boring sequences Attempted E Gym…

Codeforces GYM 100876 J - Buying roads 题解 才不是因为有了图床来测试一下呢,哼( 题意 给你\(N\)个点,\(M\)条带权边的无向图,选出\(K\)条边,使得得到的子图联通并且总代价最小,输出最小总代价和一种方案. 虽然题目里描述的很冗长,但其实这个图有一些性质:它最初是一条链/一个环,然后再有一些结点直接连到这些在链上/环上的结点.. 下图就是一个(就是样例): 做法 首先我们可以简单的查看点的度数来找到链/环上的点,和连接它们的边. 然后我们可以通过…

C - Important RoadsTime Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://acm.hust.edu.cn/vjudge/contest/view.action?cid=88926#problem/C Description The city where Georgie lives has n junctions some of which are connected by bidirectional roads. Every d…

题目传送门 题目大意: 给出一颗树,每条边都有一个颜色,对一个点来说,如果其他所有点到这个点的简单路径,相连的边颜色都不同,这个点即合法点,统计所有的合法点. 思路: 对于一个节点来说 1.如果这个节点的两个子节点的边颜色一样,那么这两个子节点的子树都要放弃. 2.如果这个节点的子节点和他的父节点的边的颜色一样,那么子节点所在子树放弃,父节点中除了这个节点以外的其他节点都要放弃. 剩下的点就是合法点. 那怎么做到放弃呢? 先dfs处理出每个节点的dfs序,每个dfs序对应的节点标号,每个节点的子…

\(\mathcal{Description}\)   Link.   给定一个含 \(n\) 个点 \(m\) 条边的简单无向图,每条边的两种定向方法各有权值,求使得图强连通且定向权值和最小的方法.   \(n\le 18\). \(\mathcal{Solution}\)   涉及到叫做"耳分解"的知识点. 有向图 \(G=(V,E)\) 是否强连通有以下判别方法: 取任意 \(u\in V\),令点集 \(S=\{u\}\): 反复取 \(x,y\in S\),以及连接 \(x,…

vp了一场gym,我又开心地划水了. A. Coloring Roads 题意:给定一棵树,树边一开始都是无色的,每次操作可以把一个点到根的路径染成某个颜色,每次询问当前树上出现过某个次数的颜色种数. 题解:看到操作与$Access$类似,考虑使用$lct$解决.由于一条重链的颜色一定是相同的,也就是一棵$splay$中的颜色都是相同的,所以$Access$时每次把整棵$splay$修改掉算一下变化就好了. #include <bits/stdc++.h> using namespace st…

poj   1251  Jungle Roads  (最小生成树) Link: http://poj.org/problem?id=1251 Jungle Roads Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 23507   Accepted: 11012 Description The Head Elder of the tropical island of Lagrishan has a problem. A b…

Jungle Roads Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 7096    Accepted Submission(s): 5185 Problem Description The Head Elder of the tropical island of Lagrishan has a problem. A burst of…

 Gym 101047M Removing coins in Kem Kadrãn Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Practice Description standard input/output Andréh and his friend Andréas are board-game aficionados. They know many of their friend…

 Gym 101047K Training with Phuket's larvae Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Practice Description standard input/output Thai cuisine is known for combining seasonings so that every dish has flavors that are…

Gym 101047E Escape from Ayutthaya Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u  Practice  Description standard input/output Ayutthaya was one of the first kingdoms in Thailand, spanning since its foundation in 1350 to…

 Gym 101047B  Renzo and the palindromic decoration Time Limit:2000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Practice Description standard input/output At the ruins of Wat Phra Si Sanphet (วดพระศรสรรเพชญ), one can find famous inscr…

Rebuilding Roads Time Limit: 1000MS   Memory Limit: 30000K Total Submissions: 11495   Accepted: 5276 Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, number 1..N) after the terrible earthquake last May. Th…

F. Constructing Roads There are N villages, which are numbered from 1 to N, and you should build some roads such that every two villages can connect to each other. We say two village A and B are connected, if and only if there is a road between A and…

Constructing Roads In JGShining's Kingdom  HDU1025 题目主要理解要用LCS进行求解! 并且一般的求法会超时!!要用二分!!! 最后蛋疼的是输出格式的注意(直接报错误!!!) #include<iostream> #include<stdio.h> #include<algorithm> #include<string.h> using namespace std; ],dp[]; int main() { ,…

题目链接 http://codeforces.com/gym/101102/problem/J Description standard input/output You are given an array A of integers of size N, and Q queries. For each query, you will be given a set of distinct integers S and two integers L and R that represent a…

题目链接 http://codeforces.com/gym/100917/problem/J Description standard input/outputStatements The jury of Berland regional olympiad in informatics does not trust to contest management systems, so the Berland regional programming contest is judged by th…

题目链接 http://codeforces.com/gym/100917/problem/D problem description Famous Berland coder and IT manager Linus Gates announced his next proprietary open-source system "Winux 10.04 LTS" In this system command "dir -C" prints list of all…

题目链接 http://codeforces.com/gym/101102/problem/D problem  description Given an R×C grid with each cell containing an integer, find the number of subrectangles in this grid that contain only one distinct integer; this means every cell in a subrectangle…

题目链接 http://codeforces.com/gym/101102/problem/C problem description Judge Bahosain was bored at ACM AmrahCPC 2016 as the winner of the contest had the first rank from the second hour until the end of the contest. Bahosain is studying the results of t…

Description Berland has n cities, the capital is located in city s, and the historic home town of the President is in city t (s ≠ t). The cities are connected by one-way roads, the travel time for each of the road is a positive integer. Once a year t…

树形DP..... Rebuilding Roads Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 8188 Accepted: 3659 Description The cows have reconstructed Farmer John's farm, with its N barns (1 <= N <= 150, number 1..N) after the terrible earthquake last Ma…