UOJ #79. 一般图最大匹配

板子：

　　

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<cstdlib>
#include<cmath>
#include<cstring>
using namespace std;
#define maxn 10010
#define llg long long 
#define yyj(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
llg n,m,sett,father[maxn],pre[maxn],match[maxn],vis[maxn],id[maxn],dl[maxn*10],head,tail,ans;

vector<llg> a[maxn];

llg find(llg x){if (father[x]!=x) father[x]=find(father[x]); return father[x];}

llg lca(llg x,llg y)
{
    sett++;
    while (vis[x]!=sett)
    {
        if (x)
        {
            x=find(x);
            if (vis[x]==sett) return x;
            vis[x]=sett;
            if (match[x]!=0) x=find(pre[match[x]]);
            else x=0;
        }
        else
        swap(x,y);
    }
    return x;
}

void change(llg x,llg y,llg fa)
{
    llg z;
    while (find(x)!=fa)
    {
        pre[x]=y; z=match[x];
        if (id[z]==1) {id[z]=0,dl[++tail]=z;}
    father[z]=fa;
    father[x]=fa;
        y=z; x=pre[y];
    }
}

bool bfs(llg p)
{
    llg x,w,v;
    for (llg i=1;i<=n;i++) id[i]=-1,father[i]=i;
    head=0,tail=1,dl[1]=p; id[p]=0;
    do
    {
        x=dl[++head],w=a[x].size();
        for (llg i=0;i<w;i++)
        {
            v=a[x][i];
            if (id[v]==-1)
            {
                pre[v]=x;
                id[v]=1;
                if (!match[v])
                {
                    llg last,t,now=v;
                    while (now!=0)
                    {
                        t=pre[now],last=match[t];
                        match[t]=now; match[now]=t;
                        now=last;
                    }//把原lai的匹配和非匹配bian取反
                    return 1;
                }
                id[match[v]]=0,dl[++tail]=match[v];
            }
            else
                if (id[v]==0 && find(v)!=find(x))
                {
                    llg dad=lca(x,v);
                    change(x,v,dad);
                    change(v,x,dad);
                }
        }
    }while (head!=tail);
    return 0;

}

void init()
{
    scanf("%lld%lld",&n,&m);
    llg x,y;
    for (llg i=1;i<=m;i++)
    {
        scanf("%lld%lld",&x,&y);
        a[x].push_back(y),a[y].push_back(x);
    }
}

int main()
{
    yyj("a");
    init();
    for (llg i=1;i<=n;i++) if (!match[i] && bfs(i)) ans++;
    cout<<ans<<endl;
    for (llg i=1;i<=n;i++) printf("%lld ",match[i]);
    return 0;
}