FZU 2150 Fire Game(bfs)

Problem 2150 Fire Game

Accept: 515    Submit: 2001
Time Limit: 1000 mSec    Memory Limit : 32768 KB

        Problem Description

Fat brother and Maze are playing a kind of special (hentai) game on an N*M board (N rows, M columns). At the beginning, each grid of this board is consisting of grass or just empty and then they start to fire all the grass. Firstly they choose two grids which are consisting of grass and set fire. As we all know, the fire can spread among the grass. If the grid (x, y) is firing at time t, the grid which is adjacent to this grid will fire at time t+1 which refers to the grid (x+1, y), (x-1, y), (x, y+1), (x, y-1). This process ends when no new grid get fire. If then all the grid which are consisting of grass is get fired, Fat brother and Maze will stand in the middle of the grid and playing a MORE special (hentai) game. (Maybe it’s the OOXX game which decrypted in the last problem, who knows.)

You can assume that the grass in the board would never burn out and the empty grid would never get fire.

Note that the two grids they choose can be the same.

    Input

The first line of the date is an integer T, which is the number of the text cases.

Then T cases follow, each case contains two integers N and M indicate the size of the board. Then goes N line, each line with M character shows the board. “#” Indicates the grass. You can assume that there is at least one grid which is consisting of grass in the board.

1 <= T <=100, 1 <= n <=10, 1 <= m <=10

   Output

For each case, output the case number first, if they can play the MORE special (hentai) game (fire all the grass), output the minimal time they need to wait after they set fire, otherwise just output -1. See the sample input and output for more details.

   Sample Input

4
3 3
.#.
###
.#.
3 3
.#.
#.#
.#.
3 3
...
#.#
...
3 3
###
..#
#.#

Sample Output

Case 1: 1
Case 2: -1
Case 3: 0
Case 4: 2

题意：
'.'表示空地，’＃‘表示草地，选两个起点火，求把草全部烧完的最小时间。

题解：
把起始两个点同时放进队列里就行了，具体的话可以理解一下bfs。

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<string>#include<algorithm>#include<cstdlib>#include<set>#include<queue>#include<stack>#include<vector>#include<map>#define N 100010#define Mod 10000007#define lson l,mid,idx<<1#define rson mid+1,r,idx<<1|1#define lc idx<<1#define rc idx<<1|1const double EPS = 1e-11;const double PI = acos(-1.0);typedef long long ll;const int INF=1000010;using namespace std;struct node{    int x, y;    int num;};vector<node>q;char mp[11][11];bool vis[11][11];int n,m,Min,ans;int xx[4]= {-1,0,1,0};int yy[4]= {0,1,0,-1};queue<node>que;void bfs(node a,node b){    while(que.size())        que.pop();    memset(vis,0,sizeof vis);    vis[a.x][a.y]=1;    vis[b.x][b.y]=1;    que.push(a);    que.push(b);    node t,tt;    while(que.size())    {        t=que.front();        ans=t.num;        que.pop();        for(int i=0; i<4; i++)        {            tt.x=t.x+xx[i];            tt.y=t.y+yy[i];            tt.num=t.num+1;            if(tt.x>=0&&tt.x<n&&tt.y>=0&&tt.y<m&&mp[tt.x][tt.y]=='#'&&!vis[tt.x][tt.y])            {                que.push(tt);                vis[tt.x][tt.y]=1;            }        }    }}int main(){    //freopen("test.in","r",stdin);    int t;    while(cin>>t)    {        int ca=1;        while(t--)        {            cin>>n>>m;            q.clear();            for(int i=0; i<n; i++)                for(int j=0; j<m; j++)                {                    cin>>mp[i][j];                    node o;                    if(mp[i][j]=='#')                    {                        o.x=i,o.y=j,o.num=0;                        q.push_back(o);                    }                }            int len=q.size();            Min=INF;            for(int i=0; i<len; i++)            {                for(int j=0; j<len; j++)                {                    ans=0;                    bfs(q[i],q[j]);                    int flag=1;                    for(int i=0; i<n; i++)                    {                        for(int j=0; j<m; j++)                            if(vis[i][j]==0&&mp[i][j]=='#')                            {                                flag=0;                                break;                            }                        if(!flag)                            break;                    }                    if(flag)                        Min=min(Min,ans);                }            }            cout<<"Case "<<ca++<<":"<<" ";            if(Min==INF)                cout<<"-1"<<endl;            else                cout<<Min<<endl;        }    }    return 0;}//Case 1: 1  Case 2: -1  Case 3: 0  Case 4: 2