hdu 4185 二分图匹配

题意用1*2的木板覆盖矩阵中的‘#’，（木板要覆盖的只能是‘#’），问最多能用几个木板覆盖

将#抽象为二分图的点，一个木板就是一个匹配，注意最后结果要除以2

Sample Input

1
6
......
.##...
.##...
....#.
....##
......

Sample Output

Case 1: 3

 

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>
using namespace std;
#define MOD 1000000007
const int INF=0x3f3f3f3f;
const double eps=1e-5;
typedef long long ll;
#define cl(a) memset(a,0,sizeof(a))
#define ts printf("*****
");
const int MAXN=1005;
int n,m,tt;
char s[MAXN][MAXN];
int uN,vN;//u,v的数目，使用前面必须赋值
int g[MAXN][MAXN];//邻接矩阵
int linker[MAXN];
bool used[MAXN];
int num[MAXN][MAXN];
bool dfs(int u)
{
    for(int v=0;v<vN;v++)
    if(g[u][v]&&!used[v])
    {
        used[v]=true;
        if(linker[v]==-1||dfs(linker[v]))
        {
            linker[v] = u;
            return true;
        }
    }
    return false;
}
int hungary()
{
    int res=0;
    memset(linker,-1,sizeof(linker));
    for(int u=0;u<uN;u++)
    {
        memset(used,false,sizeof(used));
        if(dfs(u))res++;
    }
    return res;
}
int main()
{
    int i,j,k;
    #ifndef ONLINE_JUDGE
    freopen("1.in","r",stdin);
    #endif
    int ca=0;
    scanf("%d",&tt);
    while(tt--)
    {
        scanf("%d",&n);
        cl(g);
        int tot=0;
        cl(num);
        for(i=0;i<n;i++)
        {
            scanf("%s",&s[i]);
            for(j=0;j<n;j++)
            {
                if(s[i][j]=='#')    num[i][j]=tot++;
            }
        }

        uN=vN=tot;
        for(i=0;i<n;i++)
        {
            for(j=0;j<n;j++)
            {
                if(s[i][j]=='#')
                {
                    if(s[i+1][j]=='#'&&i+1<n)  g[num[i][j]][num[i+1][j]]=1;
                    if(s[i][j+1]=='#'&&j+1<n)  g[num[i][j]][num[i][j+1]]=1;
                    if(s[i-1][j]=='#'&&i-1>=0)  g[num[i][j]][num[i-1][j]]=1;
                    if(s[i][j-1]=='#'&&j-1>=0)  g[num[i][j]][num[i][j-1]]=1;
                }
            }
        }
        ca++;
        printf("Case %d: %d
",ca,hungary()/2);
    }
}