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。

//1274，2239，2584，2536，2446
//http://wenku.baidu.com/view/9962910590c69ec3d5bb75da.html    贪心最大二分匹配 
//匈牙利树和增广轨 

#include <cstdio>
#include <cstring>

int used[610]; //是否在覆盖点中

int nmap[610][610];

int path[610];//前一个

int P,N;

int cross(int k)
{
  
  int i;
  for(i=1;i<=N;i++)
  {
    if(!nmap[k][i] || used[i])  continue;

    used[i] = 1;
    if(path[i] == -1 || cross(path[i]))
    {
      path[i] = k;
      return 1;
    }
  }
  return 0;
}

int hungray()
{
  int i;
  int nret = 0;
  memset(path,-1,sizeof(path));
  for(i=1;i<=P;i++)
  {
    if(cross(i))  nret++;
    memset(used,0,sizeof(used));
  }
  return nret;
}

int main()
{
  //freopen("in.txt","r",stdin);
  //freopen("out.txt","w",stdout);
  int tcase,i,j,a,b,c,z;
  N = 12 * 7;
  //scanf("%d",&tcase);
  while(~scanf("%d",&P))
  {
    memset(nmap,0,sizeof(nmap));
    for(i=1;i<=P;i++)
    {
      scanf("%d",&c);
      for(j=0;j<c;j++)
      {
        scanf("%d%d",&a, &b);
        z = (a-1)*12+b;
        nmap[i][z] = 1;
      }
    }
    printf("%d\n",hungray());
  }
  return 0;
}