POJ3041 Asteroids

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 using namespace std;
 6 
 7 const int maxn=505;
 8 const int maxm=10005;
 9 int N,K;
10 int Head[maxn],Adj[maxm],Next[maxm];
11 int match[maxn],use[maxn];
12 int c;
13 
14 void AddEdge(int u,int v)
15 {
16     c++;
17     Adj[c]=v;
18     Next[c]=Head[u];
19     Head[u]=c;
20 }
21 
22 bool dfs(int x)
23 {
24     for(int i=Head[x];i;i=Next[i])
25     {
26         int v=Adj[i]-N;
27         if(use[v]) continue;
28         use[v]=true;
29         if(match[v]==0||dfs(match[v]))
30         {
31             match[v]=x;
32             return true;
33         }
34     }
35     return false;
36 }
37 
38 void hungarian(int &cnt)
39 {
40     for(int i=1;i<=N;i++)
41     {
42         memset(use,false,sizeof(use));
43         if(dfs(i)) cnt++;
44     }
45 }
46 
47 int main()
48 {
49     freopen("poj3041.in","r",stdin);
50     freopen("poj3041.out","w",stdout);
51     scanf("%d %d",&N,&K);
52     int a,b;
53     for(int i=1;i<=K;i++)
54     {
55         scanf("%d %d",&a,&b);
56         AddEdge(a,b+N);
57     }
58     int cnt=0;
59     hungarian(cnt);
60     printf("%d",cnt);
61     return 0;
62 }