洛谷 1894 [USACO4.2]完美的牛栏The Perfect Stall

 1 #include<cstdio>
 2 #include<algorithm>
 3 #define N 1010
 4 #define rg register
 5 using namespace std;
 6 int n,m,E,ans,T,tot,last[N],v[N],from[N];
 7 struct edge{
 8     int to,pre;
 9 }e[N*N];
10 inline int read(){
11     int k=0,f=1; char c=getchar();
12     while(c<‘0‘||c>‘9‘)c==‘-‘&&(f=-1),c=getchar();
13     while(‘0‘<=c&&c<=‘9‘)k=k*10+c-‘0‘,c=getchar();
14     return k*f;
15 }
16 int dfs(int x){
17     for(rg int i=last[x],to;i;i=e[i].pre) if(v[to=e[i].to]!=T){
18         v[to]=T;
19         if(!from[to]||dfs(from[to])){
20             from[to]=x;
21             return 1;
22         }    
23     }
24     return 0;
25 }
26 int main(){
27     n=read(); m=read();
28     for(rg int i=1;i<=n;i++){
29         int num=read();
30         for(rg int j=1;j<=num;j++){
31             int v=read();
32             e[++tot]=(edge){v,last[i]};last[i]=tot;
33         }
34     }
35     for(rg int i=1;i<=n;i++) ++T,ans+=dfs(i);
36     printf("%d\n",ans);
37     return 0;
38 }