poj 1422 最小路径覆盖

//可转换为二分匹配
#include <iostream>
#include <cstring>
using namespace std;
#define MAXN 122

int T;
int n,m;

int G[MAXN][MAXN];

int cx[MAXN],cy[MAXN];
int sx[MAXN],sy[MAXN];

int path(int u)
{
  sx[u] = 1;
  for(int v = 1; v <= n;v++)
    {
      if(G[u][v] > 0 && (!sy[v]))
	{
	  sy[v] = 1;
	  if(!cy[v] || path(cy[v]))
	    {
	      cx[u] = v;
	      cy[v] = u;
	      return 1;
	    }
	}
    }
  return 0;
}

int MaxMatch()
{
  int res = 0;
  memset(cx,0,sizeof(cx));
  memset(cy,0,sizeof(cy));
  for(int i = 1; i <= n; i++)
    {
      if(!cx[i])
	{
	  memset(sx,0,sizeof(sx));
	  memset(sy,0,sizeof(sy));
	  res += path(i);
	}
    }
  return res;
}

int main()
{
  cin>>T;
  while(T--)
    {
      memset(G,0,sizeof(G));
      cin>>n>>m;
      while(m--)
	{
	  int x,y;
	  cin>>x>>y;
	  G[x][y] = 1;
	}
      cout<<n - MaxMatch()<<endl;
    }
  return 0;
}