POJ 3041-Asteroids-二分图匹配

 1 /*--------------------------------------------------------------------------------------*/
 2 //        Helica‘s header 
 3 //        Second Edition
 4 //        2015.11.7
 5 //
 6 #include <algorithm>
 7 #include <iostream>
 8 #include <cstring>
 9 #include <ctype.h>
10 #include <cstdlib>
11 #include <cstdio>
12 #include <vector>
13 #include <string>
14 #include <queue>
15 #include <stack>
16 #include <cmath>
17 #include <set>
18 #include <map>
19 
20 //debug function for a N*M array 
21 #define debug_map(N,M,G) printf("\n");for(int i=0;i<(N);i++)22 {for(int j=0;j<(M);j++){23 printf("%d",G[i][j]);}printf("\n");}                
24 //debug function for int,float,double,etc.
25 #define debug_var(X) cout<<#X"="<<X<<endl;
26 /*--------------------------------------------------------------------------------------*/
27 using namespace std;
28 
29 const int maxn = 500+10;
30 int uN,vN;
31 int G[2*maxn][2*maxn],linker[maxn];
32 bool used[maxn];
33 
34 bool dfs(int u)
35 {
36     for(int v=1;v<=vN;v++)
37     {
38         if(G[u][v]&& !used[v])
39         {
40             used[v] = true;
41             if(linker[v] == -1 || dfs(linker[v]))
42             {
43                 linker[v] = u;
44                 return true;
45             }
46         }
47     }
48     return false;
49 }
50 
51 int hungary()
52 {
53     int res = 0;
54     memset(linker,-1,sizeof linker);
55     for(int u=1;u<=uN;u++)
56     {
57         memset(used,false,sizeof(used));
58         if(dfs(u)) res++;
59     }
60     return res;
61 }
62 
63 int N,K,M,T;
64 
65 int main()
66 {
67     while(~scanf("%d%d",&N,&K))
68     {
69         memset(G,0,sizeof G);
70         uN = vN = N;
71         for(int i=0;i<K;i++)
72         {
73             int x,y;
74             scanf("%d%d",&x,&y);
75             G[x][y] = 1;
76         }
77         printf("%d\n",hungary());
78     }    
79 }