【算法】图论

bool spfa()
{
    memset(vis,0,sizeof(vis));
    memset(d,0x3f,sizeof(d));
    int head=0,tail=1;q[0]=S;vis[S]=1;d[S]=0;
    while(head!=tail)
     {
         int x=q[head++];if(head>3000)head=0;
         for(int i=first[x];i;i=e[i].from)
          if(d[x]+e[i].w<d[e[i].v])
           {
               int y=e[i].v;
               d[y]=d[x]+e[i].w;
               if(!vis[y])
                {
                    if(d[y]<d[q[head]]){head--;if(head<0)head=3000;q[head]=y;}
                     else{q[tail++]=y;if(tail>3000)tail=0;}
                    vis[y]=1;
                }
           }
         vis[x]=0;
     }
    return d[T];
}

void tarjan(int x)
{
    dfn[x]=low[x]=++mark;
    s[++top]=x;lack[x]=top;
    for(int i=first[x];i;i=e[i].from)
     {
         int y=e[i].v;
         if(!dfn[y])
          {
              tarjan(y);
              low[x]=min(low[x],low[y]);
          }
         else if(!col[y])low[x]=min(low[x],dfn[y]);
     }
    if(dfn[x]==low[x])
     {
         color++;
         for(int i=lack[x];i<=top;i++)col[s[i]]=color;
         num[color]=top-lack[x]+1;
         top=lack[x]-1;
     }
}
for(int i=1;i<=n;i++)if(!dfn[i])tarjan(i);

#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn=100000,maxm=100000;
struct edge{int u,v,from;}e[maxm*3];
int first[maxn],mark,dfn[maxn],low[maxn],iscut[maxn],tot,n,m;
void insert(int u,int v)
{tot++;e[tot].v=v;e[tot].u=u;e[tot].from=first[u];first[u]=tot;}
void dfs(int x,int fa)
{
    dfn[x]=low[x]=++mark;
    int child=0;
    for(int i=first[x];i;i=e[i].from)
     if(e[i].v!=fa)
     {
         int y=e[i].v;
         if(!dfn[y])
          {
              child++;//important
              dfs(y,x);
              low[x]=min(low[x],low[y]);
              if(low[y]>=dfn[x])iscut[x]=1;
          }
         else /*if(dfn[y]<dfn[x])*/low[x]=min(low[x],dfn[y]);
     }
    if(fa<0&&child<=1)iscut[x]=0;
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
     {
         int u,v;
         scanf("%d%d",&u,&v);
         insert(u,v);insert(v,u);
     }
    for(int i=1;i<=n;i++)if(!dfn[i])dfs(i,-1);
    for(int i=1;i<=n;i++)if(iscut[i])printf("%d ",i);printf("\n");
    return 0;
}