hdu 1281 棋盘游戏 二分匹配

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
const int MAXN=1024;
const int MAXM=1024*100;
int g[MAXN][MAXN],cx[MAXN],cy[MAXN],mk[MAXN];

struct Edge
{
    int from,to;
} edge[MAXM];

void init()
{
    memset(g,0,sizeof(g));
}

int dfs(int u,int m)
{
    for(int v=1; v<=m; v++)
    {
        if(!mk[v]&&g[u][v])
        {
            mk[v]=1;
            if(cy[v]==-1||dfs(cy[v],m))
            {
                cx[u]=v;
                cy[v]=u;
                return 1;
            }
        }
    }
    return 0;
}

int Maxmatch(int n,int m)
{
    int res=0;
    memset(cx,0xff,sizeof(cx));
    memset(cy,0xff,sizeof(cy));
    for(int i=1; i<=n; i++)
    {
        if(cx[i]==-1)
        {
            memset(mk,0,sizeof(mk));
            res+=dfs(i,m);
        }
    }
    return res;
}

int main()
{
    int n,m,k,i,j,u,v,ans,cnt,cas=0;
    while(~scanf("%d%d%d",&n,&m,&k))
    {
        init();
        cnt=0;
        for(i=0; i<k; i++)
        {
            scanf("%d%d",&u,&v);
            g[u][v]=1;
            edge[i].from=u;
            edge[i].to=v;
        }
        ans=Maxmatch(n,m);
        for(i=0; i<k; i++)
        {
            g[edge[i].from][edge[i].to]=0;
            if(ans!=Maxmatch(n,m))
                {
                    cnt++;
                    //printf("%d\n",i);
                }
            g[edge[i].from][edge[i].to]=1;
        }
        printf("Board %d have %d important blanks for %d chessmen.\n",++cas,cnt,ans);
    }
    return 0;
}