tarjan求割点与桥——例题（9018——2100）

#include<cstdio>
#include<iostream>
#include<cstring>
#include<vector>
using namespace std;
inline int read(){
    int num=0,t=1;char c=getchar();
    while(c>‘9‘||c<‘0‘){if(c==‘-‘)t=-1;c=getchar();}
    while(c<=‘9‘&&c>=‘0‘){num=num*10+c-‘0‘;c=getchar();}
    return num*t;
}
const int N=500010;
int dfn[N],low[N],t=0,n,m;
bool dian[N],bian[N];
struct edge{int t,num;};
vector<edge> g[N];
void dfs(int x,int fa){
    int child=0,tmp;dfn[x]=low[x]=++t;
    for(int i=0;i<g[x].size();i++){
        int y=g[x][i].t;if(y==fa){tmp=i;continue;}
        if(!dfn[y]){
            child++;dfs(y,x);
            low[x]=min(low[x],low[y]);
            if(low[y]>=dfn[x])dian[x]=1;
        }
        else low[x]=min(low[x],dfn[y]);
    }
    if(low[x]==dfn[x]&&fa!=-1)bian[g[x][tmp].num]=1;
    if(fa==-1&&child<=1)dian[x]=0;
}
int main()
{
    n=read();m=read();
    for(int i=1;i<=m;i++){
        int x=read(),y=read();
        g[x].push_back((edge){y,i});
        g[y].push_back((edge){x,i});
    }
    for(int i=1;i<=n;i++)
        if(!dfn[i])dfs(i,-1);
    for(int i=1;i<=n;i++)
        if(dian[i])printf("%d ",i);
    puts("");
    for(int i=1;i<=m;i++)
        if(bian[i])printf("%d ",i);
    return 0;
}