[边双]hihocoder 1184——边的双连通分量

题目梗概

解题思路

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=20005,maxm=200005;
int tot=-1,lnk[maxn],son[maxm],nxt[maxm];
int n,m,dfn[maxn],low[maxn],ans[maxn],tim,G,vis[maxn];
bool c[maxm],ins[maxn];
inline int _read(){
int num=0;char ch=getchar();
while(ch<'0'||ch>'9') ch=getchar();
while(ch>='0'&&ch<='9') num=num*10+ch-48,ch=getchar();
return num;
}
void add(int x,int y){nxt[++tot]=lnk[x];lnk[x]=tot;son[tot]=y;}
void tarjan(int x,int fa){
dfn[x]=low[x]=++tim;
for (int j=lnk[x];j!=-1;j=nxt[j])
if (!dfn[son[j]]){
tarjan(son[j],x);
low[x]=min(low[x],low[son[j]]);
if (low[son[j]]>dfn[x]) c[j]=1,c[j^1]=1;
}else if (son[j]!=fa) low[x]=min(low[x],dfn[son[j]]);
}
void DFS(int x){
vis[x]=G;ans[G]=min(ans[G],x);
for (int j=lnk[x];j!=-1;j=nxt[j])
if (!vis[son[j]]&&!c[j]) DFS(son[j]);
}
int main(){
freopen("exam.in","r",stdin);
freopen("exam.out","w",stdout);
n=_read(),m=_read();
memset(lnk,255,sizeof(lnk));
for (int i=1;i<=m;i++){
int x=_read(),y=_read();
add(x,y);add(y,x);
}
for (int i=1;i<=n;i++) tarjan(i,0);
memset(ans,63,sizeof(ans));
for (int i=1;i<=n;i++) if (!vis[i]) G++,DFS(i);
printf("%d\n",G);
for (int i=1;i<=n;i++) printf("%d ",ans[vis[i]]);
return 0;
}