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Lightoj 1210.cpp
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Lightoj 1210.cpp
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/*
Problem link: http://www.lightoj.com/volume_showproblem.php?problem=1210 */
#include<bits/stdc++.h>
using namespace std;
#define mx 200005
vector<int>g[mx],rg[mx],s;
int scc[mx];
int visited[mx];
int numscc;
void dfs1(int u)
{
visited[u]=1;
for(int i=0; i<g[u].size(); i++)
{
int v=g[u][i];
if(visited[v]==0) dfs1(v);
}
s.push_back(u);
}
void dfs2(int u)
{
visited[u]=1;
scc[u]=numscc;
for(int i=0; i<rg[u].size(); i++)
{
int v=rg[u][i];
if(visited[v]==0) dfs2(v);
}
}
void setting()
{
for(int i=0; i<mx; i++)
{
g[i].clear();
rg[i].clear();
visited[i]=0;
scc[i]=-1;
numscc=0;
}
s.clear();
}
int main()
{
int test;
scanf("%d",&test);
for(int cs=1; cs<=test; cs++)
{
setting();
int n;
int m;
scanf("%d%d",&n,&m);
while(m--)
{
int u,v;
scanf("%d%d",&u,&v);
g[u].push_back(v);
rg[v].push_back(u);
}
for(int i=1; i<=n; i++)
{
if(visited[i]==0)
{
dfs1(i);
}
}
memset(visited,0,sizeof visited);
reverse(s.begin(),s.end());
for(int i=0; i<n; i++)
{
if(visited[s[i]]==0)
{
dfs2(s[i]);
numscc++;
}
}
// cout<<numscc<<endl;
int in[numscc],out[numscc];
for(int i=0; i<numscc; i++) in[i]=out[i]=0;
for(int i=1; i<=n; i++)
{
for(int j=0; j<g[i].size(); j++)
{
if(scc[i]!=scc[g[i][j]])
{
in[scc[g[i][j]]]++;
out[scc[i]]++;
}
}
}
int tin=0,tout=0;
for(int i=0; i<numscc; i++)
{//cout<<in[i]<<" "<<out[i]<<endl;
if(in[i]==0) tin++;
if(out[i]==0) tout++;
}
//
int ans=max(tin,tout);
if (n == 1 || numscc == 1) ans = 0;
cout<<"Case "<<cs<<": "<<ans<<endl;
}
}