【UOJ #79】—一般图最大匹配（带花树）

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#include<bits/stdc++.h>
using namespace std;
const int RLEN=1<<20|1;
inline char gc(){
    static char ibuf[RLEN],*ib,*ob;
    (ob==ib)&&(ob=(ib=ibuf)+fread(ibuf,1,RLEN,stdin));
    return (ob==ib)?EOF:*ib++;
}
#define gc getchar
inline int read(){
    char ch=gc();
    int res=0,f=1;
    while(!isdigit(ch))f^=ch=='-',ch=gc();
    while(isdigit(ch))res=(res+(res<<2)<<1)+(ch^48),ch=gc();
    return f?res:-res;
}
#define ll long long
#define re register
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define cs const
#define bg begin
cs int N=1005,M=100005;
vector<int> e[N];
int n,m;
int id[N],pre[N],match[N],vis[N],fa[N],tim;
inline int find(int x){
	return fa[x]==x?x:fa[x]=find(fa[x]);
}
inline void add(int u,int v){
	e[u].pb(v),e[v].pb(u);
}
queue<int> q;
inline int Lca(int u,int v){
	tim++;
	while(vis[u]!=tim){
		if(u){
			u=find(u);
			if(vis[u]==tim)return u;
			vis[u]=tim;
			if(match[u]!=0)u=find(pre[match[u]]);
			else u=0;
		}
		swap(u,v);
	}
	return u;
}
inline void update(int u,int v,int z){
	while(find(u)!=z){
		pre[u]=v;int p=match[u];
		if(id[p]==1){id[p]=0,q.push(p);}
		if(find(p)==p){fa[p]=z;}
		if(find(u)==u){fa[u]=z;}
		v=p,u=pre[v];
	}
}
inline bool bfs(int s){
	for(int i=1;i<=n;i++)id[i]=-1,fa[i]=i;
	while(!q.empty())q.pop();
	q.push(s),id[s]=0;
	while(!q.empty()){
		int u=q.front();q.pop();  
		for(int &v:e[u]){
			if(id[v]==-1){
				pre[v]=u,id[v]=1;
				if(!match[v]){
					int now=v;
					while(now!=0){
						int t=pre[now],last=match[t];
						match[t]=now,match[now]=t;
						now=last;
					}
					return 1;
				}
				id[match[v]]=0,q.push(match[v]);
			}
			else if(id[v]==0&&find(u)!=find(v)){
				int lca=Lca(u,v);
				update(u,v,lca),update(v,u,lca);
			}
		}
	}
	return 0;
}
inline void solve(){
	n=read(),m=read();
	for(int i=1;i<=m;i++){
		int u=read(),v=read();
		e[u].pb(v),e[v].pb(u);
	}
	int ans=0;
	for(int i=1;i<=n;i++)if(!match[i]&&bfs(i))ans++;
	cout<<ans<<'\n';
	for(int i=1;i<=n;i++)cout<<match[i]<<" ";
}
int main(){
	solve();
}