强连通分量的模板题，第一次写tarjan算法，还不是很懂这算法吖~~~

46ms代码#include<cstdio>#include<string>#include<cmath>#include<iostream>#include<algorithm>#include<vector>#include<cstdlib>#include<map>const int INF=1<26;using namespace std;

typedef struct edge

{  int t; edge* next;}edge;

int index,bcnt,stop;

int DFN[10005],low[10005],stack[10005];edge *v[10005];bool instack[10005];

void tarjan(int i)

{  int j; edge *e; DFN[i]=low[i]=++index; instack[i]=true; stack[++stop]=i; for(e=v[i];e;e=e->next) {   j=e->t;  if(!DFN[j])  {    tarjan(j);   if(low[j]<low[i])   low[i]=low[j];  }  else if(instack[j]&&DFN[j]<low[i])  {    low[i]=DFN[j];  } } if(low[i]==DFN[i]) {   bcnt++;  do  {    j=stack[stop--];   instack[j]=false;  }  while(j!=i); }}

int main(){  int n,i,m,x,y; while(scanf("%d %d",&n,&m)&&(n!=0||m!=0)) {   edge *p[10005];  for(i=1;i<=n;i++)  {    v[i]=(edge *)malloc(sizeof(edge));   v[i]->t=i;   v[i]->next=NULL;   p[i]=v[i];  }  for(i=1;i<=m;i++)  {    scanf("%d %d",&x,&y);   p[x]->next=(edge *)malloc(sizeof(edge));   p[x]->next->t=y;   p[x]->next->next=NULL;   p[x]=p[x]->next;  }

  stop=bcnt=index=0;

  memset(DFN,0,sizeof(DFN));  memset(instack,false,sizeof(instack));  for(i=1;i<=n;i++)  {    if(!DFN[i])    tarjan(i);   if(bcnt>1)    break;  }  if(bcnt==1||n==0)   printf("Yes\n");  else   printf("No\n"); } return 0;}