P1894 [USACO4.2]完美的牛栏The Perfect Stall

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 using namespace std;
 5 int vis[2001];
 6 int head[20001];
 7 int match[10000];
 8 struct b{
 9     int to;
10     int next;
11 } e[100001];
12 int n,m;
13 int x;
14 int p;
15 int ans;
16 void add(int f,int t){
17     p++;
18     e[p].next=head[f];
19     e[p].to=t;
20     head[f]=p;
21     }
22 int y;
23 bool dfs(int f){
24     for(int i=head[f];i;i=e[i].next){
25         int v=e[i].to;
26         if(vis[v]) continue;
27         vis[v]=1;
28         if(!match[v]||dfs(match[v])){
29             match[v]=f;
30             return 1;
31         }
32     }
33     return 0;
34 }
35 int main(){
36     scanf("%d%d",&n,&m);
37     for(int i=1;i<=n;++i){
38         scanf("%d",&x);
39         for(int j=1;j<=x;++j){
40             cin>>y;
41             add(i,y);
42         }
43     }
44     for(int i=1;i<=n;++i){
45         memset(vis,0,sizeof(vis));
46         if(dfs(i)) ans++;
47     }
48     printf("%d",ans);
49     return 0;
50 }