hdu 1254 推箱子

题目：http://acm.hdu.edu.cn/showproblem.php?pid=1254

首先按箱子进行BFS.  然后判断箱子所走方向的反面，人是否能到达，即对人进行DFS。。

下面是 AC代码：

#include<iostream>
#include<cstring>
#include<queue>

using namespace std;
const int MAX = 10;
int map[MAX][MAX];
int dir[4][2]        = {{0,1},{1,0},{0,-1},{-1,0}};
int other_dir[4][2] = {{0,-1},{-1,0},{0,1},{1,0}};   //反方向
bool vis[MAX][MAX][MAX][MAX];
bool mark[MAX][MAX];
int flag,ans;
struct node
{
    int ps_x,ps_y;
    int bk_x,bk_y;
    int step;
    int cur_map[MAX][MAX];
} s_pos;
int end_x,end_y;
int m,n;
void init()
{
    s_pos.step=0;
    for(int i=0; i<m; i++) for(int j=0; j<n; j++)
        {
            if(map[i][j]==2)                s_pos.bk_x=i,  s_pos.bk_y=j;
            else if(map[i][j]==3)           end_x=i,end_y=j;
            else  if(map[i][j]==4)          s_pos.ps_x=i,  s_pos.ps_y=j;
            s_pos.cur_map[i][j]=map[i][j];
        }
    memset(vis,0,sizeof(vis));
}
bool cheak(int x,int y){
    if(x>=0&&x<m&&y>=0&&y<n&&map[x][y]!=1)        return true;  
    return false;
}
int can;
void dfs(int p_x,int p_y,int b_x,int b_y,int now_map[10][10])      //判断人能否到达箱子的旁边
{
    if(can) return ;
    if(p_x==b_x&&p_y==b_y)  {        can=1;        return ;}//cout<<p_x<<" "<<p_y<<endl;
    for(int i=0; i<4; i++){
        int x=p_x+dir[i][0],  y=p_y+dir[i][1];
        if(cheak(x,y)&&now_map[x][y]!=2&&!mark[x][y]){
            mark[x][y]=true;  dfs(x,y,b_x,b_y,now_map;  mark[x][y]=false;
        }
    }
}
void bfs()
{
    init();  queue<node > q;
    vis[s_pos.bk_x][s_pos.bk_y][s_pos.ps_x][s_pos.ps_y]=true;
    q.push(s_pos);

    while(!q.empty()){
        node now = q.front();
        q.pop();
        if(now.bk_x==end_x&&now.bk_y==end_y){
            flag=1,ans=now.step;  return ;
        }
        for(int i=0; i<4; i++){
            node next=now;
            next.bk_x+=dir[i][0],  next.bk_y+=dir[i][1];next.step+=1;
            int x=now.bk_x+other_dir[i][0],y=now.bk_y+other_dir[i][1];
            if(cheak(x,y)&&cheak(next.bk_x,next.bk_y)&&!vis[next.bk_x][next.bk_y][now.bk_x][now.bk_y])
            {
                memset(mark,0,sizeof(mark));                mark[next.ps_x][next.ps_y]=true;
                can=0;
                dfs(next.ps_x,next.ps_y,x,y,now.cur_map);
                if(can){
                    vis[next.bk_x][next.bk_y][now.bk_x][now.bk_y]=true;                    //   cout<<next.bk_x<<" "<<next.bk_y<<endl;
                    next.ps_x=now.bk_x;
                    next.ps_y=now.bk_y;
                    next.cur_map[next.bk_x][next.bk_y]=2;
                    next.cur_map[now.bk_x][now.bk_y]=0;
                    q.push(next);        
                }
            }
        }
    }
}
int main()
{

    int t,i,j;
    cin>>t;
    while(t--)
    {
        cin>>m>>n;
        for(i=0; i<m; i++) for(j=0; j<n; j++) cin>>map[i][j];
        flag=0;
        ans=-1;
        bfs();
        if(flag)   cout<<ans<<endl;
        else       cout<<-1<<endl;
    }
    return 0;

}