hdu 1254 推箱子

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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;}