Tarjan+模板

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<algorithm>
#include<iostream>
#include<set>
#include<stack>
#include<queue>
#include<map>
#include<vector>
using namespace std;

const int maxn = 105;
const int maxm = 1005;
const int inf = 0x3f3f3f3f;
const double pi = acos(-1.0);
const double eps = 1e-8;

struct Edge{
    int u,v,next;
}edge[ maxn*maxn ];
int cnt,head[ maxn ];
int vis[ maxn ],belong[ maxn ];
stack<int>s;
int dfn[ maxn ],low[ maxn ];
int Cnt ,id ;

void init(){
    while( !s.empty() )
        s.pop();
    Cnt = 0;
    id = 0;
    memset( dfn,-1,sizeof( dfn ) );
    memset( low,-1,sizeof( low ) );
    cnt = 0;
    memset( head,-1,sizeof( head ) );
}

void addedge( int a,int b ){
    edge[ cnt ].u = a;
    edge[ cnt ].v = b;
    edge[ cnt ].next = head[ a ];
    head[ a ] = cnt++;
}

void tarjan( int cur ){
    dfn[ cur ] = low[ cur ] = id++;
    vis[ cur ] = 1;
    s.push( cur );
    for( int i=head[ cur ];i!=-1;i=edge[i].next ){
        int nxt = edge[i].v;
        if( dfn[ nxt ]==-1 ){
            tarjan( nxt );
            low[ cur ] = min( low[ nxt ],low[ cur ] );
        }
        else if( vis[ nxt ]==1 ){
            low[ cur ] = min( dfn[ nxt ],low[ cur ] );
        }
    }
    if( dfn[ cur ]==low[ cur ] ){
        Cnt ++;
        while( 1 ){
            int tmp = s.top();
            s.pop();
            vis[ tmp ] = 0;
            belong[ tmp ] = Cnt;
            if( tmp==cur ) break;
        }
    }
}

int main(){
    int n,m;
    while( scanf("%d%d",&n,&m)==2 ){
        int a,b;
        init();
        while( m-- ){
            scanf("%d%d",&a,&b);
            addedge( a,b );
        }
        for( int i=1;i<=n;i++ ){
            if( dfn[i]==-1 ){
                tarjan( i );
            }
        }
        printf("缩点 = %d
",Cnt);
    }
    return 0;
}