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*],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]!=) x=find(pre[match[x]]);
             else x=;
         }
         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]==) {id[z]=,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=;i<=n;i++) id[i]=-,father[i]=i;
     head=,tail=,dl[]=p; id[p]=;
     do
     {
         x=dl[++head],w=a[x].size();
         for (llg i=;i<w;i++)
         {
             v=a[x][i];
             if (id[v]==-)
             {
                 pre[v]=x;
                 id[v]=;
                 if (!match[v])
                 {
                     llg last,t,now=v;
                     while (now!=)
                     {
                         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 ;
                 }
                 id[match[v]]=,dl[++tail]=match[v];
             }
             else
                 if (id[v]== && find(v)!=find(x))
                 {
                     llg dad=lca(x,v);
                     change(x,v,dad);
                     change(v,x,dad);
                 }
         }
     }while (head!=tail);
     return ;

 }

 void init()
 {
     scanf("%lld%lld",&n,&m);
     llg x,y;
     for (llg i=;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=;i<=n;i++) if (!match[i] && bfs(i)) ans++;
     cout<<ans<<endl;
     for (llg i=;i<=n;i++) printf("%lld ",match[i]);
     return ;
 }