标签：des style blog class code tar ext color string int art
Given a directed graph G, consider the following transformation. First, create a new graph T(G) to have the same vertex set as G. Create a directed edge between two vertices u and v in T(G) if and only if there is a path between u and v in G that follows the directed edges only in the forward direction. This graph T(G) is often called the transitive closure of G.
We define a clique in a directed graph as a set of vertices U such that for any two vertices u and v in U, there is a directed edge either from u to v or from v to u (or both). The size of a clique is the number of vertices in the clique.
The number of cases is given on the first line of input. Each test case describes a graph G. It begins with a line of two integers n and m, where 0 ≤ n ≤ 1000 is the number of vertices of G and 0 ≤ m ≤ 50,000 is the number of directed edges of G. The vertices of G are numbered from 1 to n. The following m lines contain two distinct integers u and v between 1 and n which define a directed edge from u to v in G.
For each test case, output a single integer that is the size of the largest clique in T(G).
1 5 5 1 2 2 3 3 1 4 1 5 2
4
Zachary Friggstad
强连通分量缩点成DAG,求点集最大的路径。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <algorithm> 5 #include <stack> 6 #include <vector> 7 8 using namespace std; 9 10 const int MAX_N = 1005; 11 const int edge = 5e4 + 5; 12 int N,M; 13 int low[MAX_N],pre[MAX_N],cmp[MAX_N]; 14 int first[MAX_N],Next[edge],v[edge]; 15 int ind[MAX_N],oud[MAX_N]; 16 int dfs_clock,scc_cnt; 17 int dep[MAX_N]; 18 int num[MAX_N]; 19 stack <int > S; 20 vector<int > G[MAX_N]; 21 22 23 void dfs(int u) { 24 pre[u] = low[u] = ++dfs_clock; 25 S.push(u); 26 for(int e = first[u]; e != -1; e = Next[e]) { 27 if(!pre[ v[e] ]) { 28 dfs(v[e]); 29 low[u] = min(low[u],low[ v[e] ]); 30 } else if( !cmp[ v[e] ]) { 31 low[u] = min(low[u],pre[ v[e] ]); 32 } 33 } 34 35 if(pre[u] == low[u]) { 36 ++scc_cnt; 37 for(;;) { 38 int x = S.top(); S.pop(); 39 cmp[x] = scc_cnt; 40 num[scc_cnt]++; 41 if(x == u) break; 42 } 43 } 44 } 45 void scc() { 46 dfs_clock = scc_cnt = 0; 47 memset(cmp,0,sizeof(cmp)); 48 memset(pre,0,sizeof(pre)); 49 50 for(int i = 1; i <= N; ++i) if(!pre[i]) dfs(i); 51 } 52 53 void dfs1(int u) { 54 pre[u] = 1; 55 for(int i = 0; i < G[u].size(); ++i) { 56 if(!pre[ G[u][i] ]) { 57 dfs1( G[u][i] ); 58 } 59 dep[u] = max(dep[u],dep[ G[u][i] ] + num[u]); 60 } 61 } 62 63 void solve() { 64 scc(); 65 for(int i = 1; i <= scc_cnt; ++i) G[i].clear(); 66 for(int i = 1; i <= scc_cnt; ++i) dep[i] = num[i]; 67 68 for(int i = 1; i <= N; ++i) { 69 for(int e = first[i]; e != -1; e = Next[e]) { 70 if(cmp[i] == cmp[ v[e] ]) continue; 71 G[ cmp[i] ].push_back(cmp[ v[e] ]); 72 } 73 } 74 75 memset(pre,0,sizeof(pre)); 76 for(int i = 1; i <= scc_cnt; ++i) { 77 if(!pre[i]) dfs1(i); 78 } 79 80 int ans = 0; 81 for(int i = 1; i <= scc_cnt; ++i) { 82 ans = max(ans,dep[i]); 83 } 84 85 printf("%d\n",ans); 86 87 } 88 89 void add_edge(int id,int u) { 90 int e = first[u]; 91 Next[id] = e; 92 first[u] = id; 93 } 94 int main() 95 { 96 //freopen("sw.in","r",stdin); 97 int t; 98 scanf("%d",&t); 99 while(t--) { 100 scanf("%d%d",&N,&M); 101 for(int i = 1; i <= N; ++i) first[i] = -1; 102 memset(num,0,sizeof(num)); 103 104 for(int i = 1; i <= M; ++i) { 105 int u; 106 scanf("%d%d",&u,&v[i]); 107 add_edge(i,u); 108 } 109 110 solve(); 111 } 112 //cout << "Hello world!" << endl; 113 return 0; 114 }
标签：des style blog class code tar ext color string int art
原文地址：http://www.cnblogs.com/hyxsolitude/p/3700877.html
