HDU-1150 HK二分图最小点覆盖

//二分图最小点覆盖 = 二分图最大匹配

#include
#include
#include
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
{
    queueque;
    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 k,x,y;
    while( scanf("%d",&nx ) != EOF , nx )
    {
        scanf("%d%d",&ny,&m);
        memset( map,0,sizeof(map) );
        for( int i = 1; i <= m; i++ )
        {
            scanf("%d%d%d",&k,&x,&y);
            map[x][y] = 1;
        }
        printf("%d\n", MaxMatch() );
    }
}