tarjan 強聯通分量和割點

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 1 #include<cstdio>  2 #include<cstring> 3 #include<cmath> 4 #include<ctime> 5 #include<iostream> 6 #include<algorithm> 7 #include<queue> 8 #include<stack> 9 #include<set>10 #define esp (1e-6)11 #define inf (0x3f3f3f3f)12 #define l(a) ((a)<<1)13 #define r(a) ((a)<<1|1)14 #define b(a) (1<<(a))15 #define rep(i,a,b) for(int i=a;i<=(b);i++)16 #define clr(a) memset(a,0,sizeof(a))17 typedef long long ll;18 typedef unsigned long long ull;19 using namespace std;20 int readint(){21     int t=0,f=1;char c=getchar();22     while(!isdigit(c)){23         if(c==‘-‘) f=-1;24         c=getchar();25     }26     while(isdigit(c)){27         t=(t<<3)+(t<<1)+c-‘0‘;28         c=getchar();29     }30     return t*f;31 }32 const int maxn=100009,maxm=200009;33 struct edge{34     int v;35     edge*next;36 }e[maxm],*pt=e,*fir[maxn];37 int n,m,ans,dfstime,scccnt,size[maxn],pre[maxn],low[maxn],scc[maxn];38 bool p[maxn];39 void add(int u,int v){40     pt->v=v;pt->next=fir[u];41     fir[u]=pt++;42 }43 void addedge(int u,int v){44     add(u,v);add(v,u);45 }46 stack<int>S;47 void dfs(int x,int f){48     int son=0;49     pre[x]=low[x]=++dfstime;S.push(x);50     for(edge*e=fir[x];e;e=e->next) if(e->v!=f){51         if(!pre[e->v]){52             son++;dfs(e->v,x);53             low[x]=min(low[x],low[e->v]);54             if(f!=-1&&low[e->v]>=pre[x]) p[x]=1;55         }else if(!scc[e->v]) low[x]=min(low[x],pre[e->v]);56     }57     if(f==-1&&son>1) if(!p[x]) p[x]=1;58     if(pre[x]==low[x]){59         int t=-1;++scccnt;60         while(t!=x){61             t=S.top();S.pop();62             scc[t]=scccnt;size[scccnt]++;63         }64     }65 }66 void tarjan(){67     rep(i,1,n) if(!scc[i]) dfs(i,-1);68     rep(i,1,n) if(p[i]) ans++;69     cout<<ans<<endl;70     rep(i,1,n) if(p[i]){71         ans--;printf("%d",i);72         putchar(ans?‘ ‘:‘\n‘);73     }74 }75 int main(){76     //freopen("#input.txt","r",stdin);77     //freopen("#output.txt","w",stdout);78     n=readint();m=readint();79     rep(i,1,m){80         int U=readint(),V=readint();81         addedge(U,V);82     }83     tarjan();84     //fclose(stdin);85     //fclose(stdout);86     return 0;87 }

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tarjan 強聯通分量和割點