[poj] 3057 Evacuation

#include<cstdio>
#include<queue>
#include<cstring>
#define pos(x,y) (x-1)*m+y
using namespace std;
int n,m,T,cnt,dx[]={0,1,0,-1,0},dy[]={0,0,1,0,-1},dis[50][150],lover[150],person,door,vis[15][15],p,QWQ;
bool v[150],mp[50][150],b;
char s[15][15];
queue <int> qx,qy,t;

void init()
{
    door=person=0;
    cnt=0;
    p=b=0;
    memset(dis,0,sizeof(dis));
    memset(vis,0,sizeof(vis));
    memset(lover,0,sizeof(lover));
}

void bfs(int x,int y)
{
    ++door;
    int rx,ry,tt;
    qx.push(x);
    qy.push(y);
    t.push(0);
    vis[x][y]=cnt;
    while (!qx.empty())
    {
    rx=qx.front();ry=qy.front();tt=t.front();
    qx.pop();qy.pop();t.pop();
    for (int i=1;i<=4;i++)
    {
        if (s[rx+dx[i]][ry+dy[i]]=='.' && vis[rx+dx[i]][ry+dy[i]]!=cnt)
        {
        vis[rx+dx[i]][ry+dy[i]]=cnt;
        qx.push(rx+dx[i]);qy.push(ry+dy[i]);t.push(tt+1);
        dis[door][pos(rx+dx[i],ry+dy[i])]=tt+1;
        }
    }
    }
}

void getmap(int t)
{
    for (int i=1;i<=n;i++)
    for (int j=1;j<=m;j++)
        for (int k=1;k<=door;k++)
        if (dis[k][pos(i,j)] && dis[k][pos(i,j)]<=t && s[i][j]=='.')
            mp[k][pos(i,j)]=1;
        else mp[k][pos(i,j)]=0;
}

bool find(int x)
{
    for (int i=1;i<=n*m;i++)
    {
    if (!v[i] && mp[x][i])
    {
        v[i]=1;
        if (!lover[i] || find(lover[i]))
        {
        lover[i]=x;
        return 1;
        }
    }
    }
    return 0;
}

int main()
{
    scanf("%d",&QWQ);
    while (QWQ--)
    {
    scanf("%d%d",&n,&m);
    init();
    for (int i=1;i<=n;i++)
        scanf("%s",s[i]+1);
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
        if (s[i][j]=='D') ++cnt,bfs(i,j);
        else if (s[i][j]=='.') ++person;
    for (int i=1;i<=n*m;i++)
    {
        getmap(i);
        for (int j=1;j<=door;j++)
        {
        memset(v,0,sizeof(v));
        if (find(j)) p++;
        }
        if (p==person)
        {
        printf("%d\n",i);
        b=1;
        break;
        }
    }
    if (!b) printf("impossible\n");
    }
    return 0;
}