POJ 3041 Asteroids（二分图 && 匈牙利算法 && 最小点覆盖）

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 
 5 using namespace std;
 6 
 7 int match[505], vis[505], g[505][505], n;
 8 
 9 inline int dfs(int u){
10     for(int i = 1; i <= n; i++){
11         if(g[u][i] && !vis[i]){
12             vis[i] = 1;
13             if(!match[i] || dfs(match[i])){
14                 match[i] = u;
15                 return 1;
16             }
17         }
18     }
19     return 0;
20 }//匈牙利
21 
22 inline int hungary(){
23     int ans = 0;
24     for(int i = 1; i <= n; i++){
25         memset(vis, 0, sizeof(vis));
26         if(dfs(i)) ans++;
27     }
28     return ans;
29 }
30 
31 int main(){
32     int k;
33     while(~scanf("%d%d", &n, &k)){
34         for(int i = 1; i <= k; i++){
35             int r, c;
36             scanf("%d%d", &r, &c);
37             g[r][c] = 1;
38         }
39         printf("%d\n", hungary());
40     }
41     return 0;
42 }