poj 2239 Selecting Courses

确定用二分图算法，就找好对应关系，本题对应关系为一周的所有课节N=7*12，和每一科的对应。

 1 //1274，2239，2584，2536，2446

 2 //http://wenku.baidu.com/view/9962910590c69ec3d5bb75da.html    贪心最大二分匹配 

 3 //匈牙利树和增广轨 

 4 

 5 #include <cstdio>

 6 #include <cstring>

 7 

 8 int used[610]; //是否在覆盖点中

 9 

10 int nmap[610][610];

11 

12 int path[610];//前一个

13 

14 int P,N;

15 

16 int cross(int k)

17 {

18   

19   int i;

20   for(i=1;i<=N;i++)

21   {

22     if(!nmap[k][i] || used[i])  continue;

23 

24     used[i] = 1;

25     if(path[i] == -1 || cross(path[i]))

26     {

27       path[i] = k;

28       return 1;

29     }

30   }

31   return 0;

32 }

33 

34 int hungray()

35 {

36   int i;

37   int nret = 0;

38   memset(path,-1,sizeof(path));

39   for(i=1;i<=P;i++)

40   {

41     if(cross(i))  nret++;

42     memset(used,0,sizeof(used));

43   }

44   return nret;

45 }

46 

47 int main()

48 {

49   //freopen("in.txt","r",stdin);

50   //freopen("out.txt","w",stdout);

51   int tcase,i,j,a,b,c,z;

52   N = 12 * 7;

53   //scanf("%d",&tcase);

54   while(~scanf("%d",&P))

55   {

56     memset(nmap,0,sizeof(nmap));

57     for(i=1;i<=P;i++)

58     {

59       scanf("%d",&c);

60       for(j=0;j<c;j++)

61       {

62         scanf("%d%d",&a, &b);

63         z = (a-1)*12+b;

64         nmap[i][z] = 1;

65       }

66     }

67     printf("%d\n",hungray());

68   }

69   return 0;

70 }