poj 2239 Selecting Courses

二分图基础。

求二分图最大匹配（匈牙利算法）。

View Code

 1 /*

 2 Author:Zhaofa Fang

 3 Lang:C++

 4 */

 5 #include <cstdio>

 6 #include <cstdlib>

 7 #include <iostream>

 8 #include <cmath>

 9 #include <cstring>

10 #include <algorithm>

11 #include <string>

12 #include <vector>

13 #include <queue>

14 #include <stack>

15 #include <map>

16 #include <set>

17 #define pb push_back

18 using namespace std;

19 

20 //==========================================

21 //二分图最大匹配

22 

23 const int maxn=305;

24 bool maz[maxn][maxn],vist[maxn];

25 int match[maxn],n,m;

26 

27 bool dfs(int u)

28 {

29     for(int v=1;v<=m;v++)

30     {

31         if(maz[u][v] && !vist[v])

32         {

33             vist[v]=true;

34             if(match[v] == -1 || dfs(match[v]))

35             {

36                 match[v]=u;

37                 return true;

38             }

39         }

40     }

41     return false;

42 }

43 

44 int Match()

45 {

46     int cnt=0;

47     memset(match,-1,sizeof(match));

48     for(int u=1;u<=n;u++)

49     {

50         memset(vist,false,sizeof(vist));

51         if(dfs(u))cnt++;

52     }

53     return cnt;

54 }

55 

56 int main()

57 {

58     while(~scanf("%d",&n))

59     {

60         memset(maz,0,sizeof(maz));

61         m=0;

62         for(int i=1;i<=n;i++)

63         {

64             int t;

65             scanf("%d",&t);

66             while(t--)

67             {

68                 int q,p;

69                 scanf("%d%d",&q,&p);

70                 maz[i][q*12+p]=true;

71                 m=max(m,q*12+p);

72             }

73         }

74         printf("%d\n",Match());

75     }

76     return 0;

77 }