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CF711D Directed Roads 题解

Description 洛谷传送门 Solution 看到 $n$ 个点 $n$ 条边，显然的基环树（可能是基环树森林），所以我们对于环上的点和非环上的点分别处理。假设一共有 $cnt$ 个环，每个环上有 $d_i$ 个点，我们来分类讨论一下：对于环上的点，我们发现只有两种情况会产生环，即 \(1 \rightarrow 2

论文学习：Directed Greybox Fuzzing（CCS‘17）

INTRODUCTION 本文引入了定向模糊测试（DGF），专注于到达程序中给定的目标位置。在高层次上，本文将可达性视为算法中的优化问题，并采用特定的元启发式，以最大限度地缩短生成的种子和目标的距离。为了计算种子距离，本文首先计算并插桩每个基本块到目标的距离。虽然种子距离是程

基环树学习笔记 & CF711D Directed Roads

传送门基环树定义： n个节点n条边的连通图。性质：很显然有且仅有一个环。如何找环： dfs，每次读到一个节点入栈（类似Tarjan）拓扑排序：最后剩下的度数不为零的点一定就在环上题目通常解法：把环看做一个整个树的根，然后把子树的信息挂到环的每一个点上，问题变成了环上操作，再根据题目

F. Graph Without Long Directed Paths

传送门题意：对每条边定向，使得图中不存在长度为2的路径。分析：相当于对每个点颜色，类似于二分图染色。然后再check一下合法性即可。 c o d e

[atARC121E]Directed Tree

令$b_{a_{i}}=i$，那么问题即要求$i$不是$b_{i}$的祖先，也即$b_{i}$不严格在$i$的子树中显然$a_{i}$和$b_{i}$一一对应，因此我们不妨统计$b_{i}$的个数考虑容斥，令$f(S)$为$\forall i\in S,b_{i}$严格在$i$子树中的排列数，根据容斥答案即$\sum_{S\subseteq [1,n]}(-1)^{|S|}f(S)$ 关于

CF711D Directed Roads

【题意】有 n 个点和 n 条边，第 i 条边从 i 连到 ai 。每条边需要指定一个方向（无向边变为有向边）。问有多少种指定方向的方案使得图中不出现环【分析】题目给定的是一个基环树森林，要求我们把无向边定向，问不包含环的方案数显然这个环只能来自基环树的环考虑一棵基环树，只要环上

Proj THUDBFuzz Paper Reading: Sequence Directed Hybrid Fuzzing

Abstract 技术: sequence directed + concolic execution 工具: Berry 实验: 比较对象: BugRedux, AFLGo, LOLLY, QSYM 效果: outperforms 找到7个CVEs Intro enhance the target seq with statements which must be explored before the necessary nodes 用在到达目标序列之

寻找图中的有向环-java

判断图中是否有一个有向环： edgeTo 数组找到有向环的所有顶点 onStack 调用dfs时将其设置为true，调用结束时设为false。 public class DirectedCycle { private boolean[] marked; // marked[v] = has vertex v been marked? private int[] edgeTo; /

Go-directed and habitual learning

行为心理学行为心理学由instrumental conditioning(operant conditioning)和respondent behaviors(classical conditioning; Pavlovian)共同构成。两者区别在于stimuli和response是voluntary 还是involuntary。 Classical conditioning 典型的代表是巴普洛夫的狗，中性条件（铃

ALG 3-5: Connectivity in Directed Graphs (有向图的连接性)

Directed Graphs Directed graph. G = (V, E) Edge (u, v) goes from node u to node v. Ex. Web graph -hyperlink points from one web page to another. （网络图——从一个网页到另一个网页的超链接） Directedness of graph is crucial. （图的方向性至关重要） Modern web se

Codeforces Round #656 (Div. 3)E. Directing Edges(拓扑排序+构造dag图)

题目大意给你$n$个定点$m$条边，这$m$条边中有有向边也有无向边。当$t=0$时，输入边代表的是无向边。当$t=1$时，输入的边代表的是$x->y$的有向边。要你将所有的无向边变为有向边后整个图是无环的(有向无环图)。思路有向边时建边而且更新入度，无向边时只存边不更新入度

G - Longest Path

Problem Statement There is a directed graph GG with NN vertices and MM edges. The vertices are numbered 1,2,…,N1,2,…,N, and for each ii (1≤i≤M1≤i≤M), the ii-th directed edge goes from Vertex xixi to yiyi. GG does not contain directed cyc

Codeforces 1144F Graph Without Long Directed Paths DFS染色

题意：输入一张有向图，无自回路和重边，判断能否将它变为有向图，使得图中任意一条路径长度都小于2。如果可以，按照输入的边的顺序输出构造的每条边的方向，构造的边与输入的方向一致就输出1，否则输出0。题解：当我看到“图中任意一条路径长度都小于2”这句话的时候我都懵了，不知道这道题

Codechef MAY 15 Counting on a directed graph

题目大意给定一张 n 个点 m 条边的有向图，一个点对 (X,Y) 是合法的当且仅当存在一条从 1 到 X 的路径，一条从 1到 Y 的路径满足它们除了 1 号点以外没有任何公共点。统计合法的无序对(X,Y) 的个数。数据范围 n ≤ 105, m ≤ 5 × 105 吉如一的题解可以发现一个点对 (X, Y ) 是

基于JGraphT实现的路径探寻

基于JGraphT实现的路径探寻业务中提出基于内存，探寻的两点间的有向以及无向路径，多点间的最小子图等需求，以下记录使用JGraphT的实现过程。 GraphT是免费的Java类库，提供数学图论对象和算法，本文只涉及路径探寻中的部分内容。图实例简介以下资料来源graph-structures 可用图概览

数据结构期末图

基本概念 A directed graph is called strongly connected if there is a directed path from any vertex to any other vertex. If we suppress the direction of the edges and the resulting undirected graph is connected, we call the directed graph weakly connecte

CF711D 【Directed Roads】

这是一场比赛的 T4T4 ,身为蒟蒻的我当然没有想出来。后来对基环树有了一点了解之后就来肝这道题。首先对于一条边，只有两种情况 1.在环上，那么这个环只有全部正向或全部反向才可以成立，而总方案数显然是 2m ，其中 mm 是环上的边数，所以方案数就是 2m-2 2.不在环上，那么这种边就

Detect cycle in a directed graph

Question: Detect cycle in a directed graph Answer: Depth First Traversal can be used to detect cycle in a Graph. DFS for a connected graph produces a tree. There is a cycle in a graph only if there is a back edge present in the graph. A back edge is an ed

Directed Roads CodeForces - 711D (基环外向树 )

ZS the Coder and Chris the Baboon has explored Udayland for quite some time. They realize that it consists of n towns numbered from 1 to n. There are n directed roads in the Udayland. i-th of them goes from town i to some other town ai (ai ≠ i). ZS the Co

Graph Without Long Directed Paths CodeForces - 1144F 题解

Graph Without Long Directed Paths CodeForces - 1144F题目题目分析代码题目 You are given a connected undirected graph consisting of n vertices and m edges. There are no self-loops or multiple edges in the given graph. You have to direct its edges in such

POJ-1308 Is It A Tree?（直接写的题）

加油。 To be better. 题目链接： https://cn.vjudge.net/problem/POJ-1308 题目： A tree is a well-known data structure that is either empty (null, void, nothing) or is a set of one or more nodes connected by directed edges between nodes satisfying the followi

复杂网络-标准公开数据集

http://vlado.fmf.uni-lj.si/pub/networks/data/ SNAP（Stanford Large Network Dataset Collection）实验数据集主要包含以下数据集 Social networks : online social networks, edges represent interactions between people Networks with ground-truth communities :

Codeforces Round #550 (Div. 3) F. Graph Without Long Directed Paths

F. Graph Without Long Directed Paths 题目链接：https://codeforces.com/contest/1144/problem/F 题意：给出一个无向图，现在要求你给边定向，使得这个图中任意一条路径的长度都不超过1，最后输出一种方法即可。题解：易知出现奇环时最后不满足条件，所以可以联想到黑白染色来判断可