POJ 3057 Evacuation | 二分图匹配

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<vector>
#include<queue>
#define N 400
using namespace std;
int t,n,m,dis[N][N],vis[N],dx[5]={1,0,-1,0};
int dy[5]={0,1,0,-1};
int d_cnt,ans,adj[N][N],V[N],live,tot,bf[N];
char mp[N][N];
queue <int> qx,qy;
inline int get(int x,int y) {return m*(x-1)+y;}
void add(int T)
{
    for (int i=1;i<=n;i++)
    for (int j=1;j<=m;j++)
        for (int k=1;k<=d_cnt;k++)
        if (mp[i][j]=='.' && dis[k][get(i,j)]<=T)
           adj[k][get(i,j)]=1;
}
void BFS(int X,int Y)
{
    ++d_cnt;
    qx.push(X),qy.push(Y);
    memset(vis,-1,sizeof(vis));
    vis[get(X,Y)]=0;
    while (!qx.empty())
    {
    int x=qx.front(),y=qy.front();
    for (int i=0;i<4;i++)
    {
        int xx=x+dx[i],yy=y+dy[i];
        if (mp[xx][yy]=='.' && vis[get(xx,yy)]==-1)
        {
        qx.push(xx),qy.push(yy);
        vis[get(xx,yy)]=vis[get(x,y)]+1;
        dis[d_cnt][get(xx,yy)]=vis[get(xx,yy)];
        }
    }
    qx.pop(),qy.pop();
    }
}
int find(int x)
{
    for (int i=1;i<=n*m;i++)
    {
    if (!V[i] && adj[x][i]==1)
    {
        V[i]=1;
        if (!bf[i] || find(bf[i]))
        {
        bf[i]=x;
        return 1;
        }
    }
    }
    return 0;
}
void init()
{
    memset(dis,127,sizeof(dis));
    memset(adj,0,sizeof(adj));
    memset(bf,0,sizeof(bf));
    d_cnt=0;
    live=0;
    ans=0;
}
int main()
{
    scanf("%d",&t);
    while (t--)
    {
    init();
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)
        scanf("%s",mp[i]+1);
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
        if (mp[i][j]=='D')
            BFS(i,j);
        else if (mp[i][j]=='.') live++;
    for (int k=1;k<=150;k++)
    {
        add(k);
        for (int i=1;i<=d_cnt;i++)
        {
        memset(V,0,sizeof(V));
        if (find(i)) ans++;
        }
        if (ans==live)
        {
        printf("%d
",k);
        break;
        }
    }
    if (ans!=live)
        puts("impossible");
    }
    return 0;
}