Hopcroft-Karp算法 二分图最小路径覆盖

//二分图最小路径覆盖 = 顶点数 - 最大匹配
#include<stdio.h>
#include<string.h>
#include<queue>
using namespace std;
const int maxn = 105;
const int inf = 1<<30;
int nx,ny,m;
int dis;
int map[maxn][maxn];
int cx[maxn],cy[maxn];
int dx[maxn],dy[maxn];
bool vis[maxn];

//Hopcroft-Karp算法 有点类似dinic 都是先对图BFS分层再沿层数DFS找增广路
//***************************************************************************
bool searchpath()      //BFS 对二分图分层
{
queue<int>que;
dis = inf;
memset( dx,-1,sizeof(dx) );
memset( dy,-1,sizeof(dy) );
for( int i = 1; i <= nx; i ++ )   //找到x集合所有未被匹配的点压入队列中
{
if( cx[i] == -1 )
{
que.push(i);
dx[i] = 0;
}
}
while( !que.empty() )
{
int u = que.front(); que.pop();
if( dx[u] > dis )
break;
for( int v = 1; v <= ny; v ++ )
{
if( map[u][v] && dy[v] == -1 )
{
dy[v] = dx[u] + 1;
if( cy[v] == -1 )
dis = dy[v];
else
{
dx[cy[v]] = dy[v] + 1;
que.push( cy[v] );
}
}
}
}
return dis != inf;
}

bool findpath( int u )   //沿着层数DFS
{
for( int v = 1; v <= ny; v ++ )
{
if( map[u][v] && !vis[v] && dy[v] == dx[u] + 1 )
{
vis[v] = 1;
if( cy[v] != -1 && dy[v] == dis )
continue;
if( cy[v] == -1 || findpath( cy[v] ) )
{
cy[v] = u;
cx[u] = v;
return true;
}
}
}
return false;
}
int MaxMatch()
{
int ans = 0;
memset( cx,-1,sizeof(cx) );
memset( cy,-1,sizeof(cy) );
while( searchpath() )
{
memset( vis,0,sizeof(vis) );
for( int i = 1; i <= nx; i ++ )
{
if( cx[i] == -1 )
{

ans += findpath( i );
}
}
}
return ans;
}
//****************************************************************

int main()
{
int t,x,y;
scanf("%d",&t );
while( t-- )
{
scanf("%d%d",&ny,&m);
nx = ny;
memset( map,0,sizeof(map) );
for( int i = 1; i <= m; i++ )
{
scanf("%d%d",&x,&y);
map[x][y] = 1;
}
printf("%d\n", nx-MaxMatch() );
}
}