课程-二分图

 1 #include<iostream>
 2 #include<vector>
 3 #include<queue>
 4 #include<cstring>
 5 using namespace std;
 6 const int maxn=100010;
 7 const int inf=1<<30;
 8 struct Edge{
 9     int from,to,flow,cap;
10 };
11 struct Dinic{
12     int vis[maxn],cur[maxn],d[maxn];
13     vector<Edge> edges;
14     vector<int> G[maxn];
15     int s,t;
16     void clear()
17     {
18         for(int i=0;i<maxn;i++) G[i].clear();
19         edges.clear();
20     }
21     void addEdge(int from,int to,int cap)
22     {
23         edges.push_back((Edge){from,to,0,cap});
24         G[from].push_back(edges.size()-1);
25         edges.push_back((Edge){to,from,0,0});
26         G[to].push_back(edges.size()-1);
27     }
28     int BFS()
29     {
30         memset(vis,0,sizeof(vis));
31         queue<int> Q;
32         Q.push(s);
33         vis[s]=1;
34         d[s]=0;
35         while(!Q.empty()){
36             int x=Q.front();Q.pop();
37             for(int i=0;i<G[x].size();i++){
38                 Edge& e=edges[G[x][i]];
39                 if(!vis[e.to]&&e.cap>e.flow){
40                     vis[e.to]=1;
41                     d[e.to]=d[x]+1;
42                     Q.push(e.to);
43                 }
44             }
45         }
46         return vis[t];
47     }
48     int DFS(int u,int a)
49     {
50         if(u==t||a==0) return a;
51         int flow=0,f;
52         for(int& i=cur[u];i<G[u].size();i++){
53             Edge& e=edges[G[u][i]];
54             if(d[e.to]==d[u]+1&&(f=DFS(e.to,min(a,e.cap-e.flow)))>0){
55                 e.flow+=f;
56                 edges[G[u][i]^1].flow-=f;
57                 flow+=f;
58                 a-=f;
59                 if(!a) break;
60             }
61         }
62         return flow;
63     }
64     int MaxFlow(int ss,int tt)
65     {
66         int ans=0;
67         s=ss,t=tt;
68         while(BFS()){
69             memset(cur,0,sizeof(cur));
70             ans+=DFS(s,inf);
71         }
72         return ans;
73     }
74 };
75 Dinic solver;
76 int main()
77 {
78     int n,p,T,m,a;
79     cin>>T;
80     while(T--)
81     {
82         solver.clear();
83         cin>>p>>n;
84         for(int i=2;i<=n+1;i++) solver.addEdge(1,i,1);
85         for(int i=n+2;i<=n+p+1;i++) solver.addEdge(i,n+p+2,1);
86         for(int i=1;i<=p;i++){
87             cin>>m;
88             while(m--){
89                 cin>>a;
90                 solver.addEdge(a+1,n+i+1,1);
91             }
92         }
93         if(solver.MaxFlow(1,n+p+2)==p) cout<<"YES\n";
94         else cout<<"NO\n";
95     }
96     return 0;
97 }