hdu 1254 推箱子(BFS+BFS或BFS+DFS)

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题意：

想法：

先用BFS将箱子向前推，在每次推箱子前有BFS或DFS判断人是否能到达箱子后面；

代码实现：

一 BFS+BFS实现：（时间：0ms）

#include <iostream>#include <cstdio>#include <cstring>#include <queue>using namespace std;const int MAX=9;int n,m,Map[MAX][MAX];bool Visted[MAX][MAX],Walk[MAX][MAX][MAX][MAX];int sx1,sy1,spx,spy;int Move[4][2]={{1,0},{-1,0},{0,1},{0,-1}};struct Node{    int x,y,step;    int px,py;}Q[MAX*MAX];struct Stack{    int x,y;}S[MAX*MAX];bool Judge( int x, int y ){     if( x<=0 || y<=0 || x>m || y>n || Map[x][y]==1 )       return false;     return true;}bool BFS( int x, int y, int px, int py, int x1, int y1 ){    if( x==px && y==py )      return 1;    memset(Visted,0,sizeof(Visted));    Visted[x1][y1]=1;    int front=0,tail=1;    S[0].x=x;    S[0].y=y;    while( front<tail )    {        Stack Now=S[front++];        for( int i=0; i<4; ++i )        {           Stack Next;           Next.x=Now.x+Move[i][0];           Next.y=Now.y+Move[i][1];           if( Judge(Next.x,Next.y) && !Visted[Next.x][Next.y] )           {               Visted[Next.x][Next.y]=1;               S[tail++]=Next;               if( Next.x==px && Next.y==py )                   return 1;           }        }    }    return 0;} void BFS(){   Node p1;   p1.x=sx1;   p1.y=sy1;   p1.step=0;   p1.px=spx;   p1.py=spy;   int front=0,tail=1;   Q[0]=p1;   while( front<tail )   {       Node Now=Q[front++];       for( int i=0; i<4; ++i )       {           Node Next;           Next.x=Now.x+Move[i][0];           Next.y=Now.y+Move[i][1];           Next.px=Now.x;           int x=Now.x-Move[i][0];           Next.py=Now.y;           int y=Now.y-Move[i][1];           Next.step=Now.step+1;           if( Judge(Next.x,Next.y) && Judge(x,y) && BFS(Now.px,Now.py,x,y,Now.x,Now.y) )           {                if( Map[Next.x][Next.y]==3 )                {                     printf("%d\n",Next.step);                     return;                }                if( !Walk[Next.x][Next.y][Next.px][Next.py] )                {                    Walk[Next.x][Next.y][Next.px][Next.py]=1;                    Q[tail++]=Next;                }           }       }   }   printf("-1\n");}int main(){    //freopen("in.txt","r",stdin);    int t;    scanf("%d",&t);    while( t-- )    {        scanf("%d%d",&m,&n);        for( int i=1; i<=m; ++i )        {            for( int j=1; j<=n; ++j )            {                scanf("%d",&Map[i][j]);                if( Map[i][j]==2 )                {                    sx1=i;                    sy1=j;                }                else if( Map[i][j]==4 )                {                    spx=i;                    spy=j;                   // Map[i][j]=0;                }            }        }        memset(Walk,0,sizeof(Walk));        Walk[sx1][sy1][spx][spy]=1;        BFS();    }    return 0;}

二 BFS+DFS实现（时间625ms）

#include <iostream>#include <cstdio>#include <cstring>#include <queue>using namespace std;const int MAX=8;int n,m,Map[MAX][MAX];bool Visted[MAX][MAX],Walk[MAX][MAX][MAX][MAX],flag;int sx1,sy1,spx,spy;int Move[4][2]={{1,0},{-1,0},{0,1},{0,-1}};struct Node{    int x,y,step,dir;    int px,py;}Q[MAX*MAX];struct Stack{    int x,y;}S[MAX*MAX];void DFS( int x, int y ){    if( flag )      return;    if( x==spx && y==spy )    {        flag=1;        return;    }    for( int i=0; i<4; ++i )    {        int x1=x+Move[i][0];        int y1=y+Move[i][1];        if( x1<=0 || y1<=0 || x1>m || y1>n || Map[x1][y1]==1 )          continue;        if( !Visted[x1][y1] )        {            Visted[x1][y1]=1;            DFS(x1,y1);            Visted[x1][y1]=0;        }        if( flag )         return;    }}void BFS(){   Node p1;   p1.x=sx1;   p1.y=sy1;   p1.step=0;   p1.dir=-1;   p1.px=spx;   p1.py=spy;   int front=0,tail=0;   Q[tail++]=p1;   while( front<tail )   {       Node Now=Q[front++];       for( int i=0; i<4; ++i )       {           Node Next;           Next.dir=i;           Next.x=Now.x+Move[i][0];           Next.y=Now.y+Move[i][1];           Next.px=Now.x;           int x=Now.x-Move[i][0];           Next.py=Now.y;           int y=Now.y-Move[i][1];           Next.step=Now.step+1;           if( Next.x<=0 || Next.y<=0 || Next.x>m || Next.y>n               || Map[Next.x][Next.y]==1 )             continue;           if( x<=0 || y<=0 || x>m || y>n              || Map[x][y]==1 )             continue;               memset(Visted,0,sizeof(Visted));               Visted[Now.x][Now.y]=1;               spx=x;               spy=y;               flag=0;               DFS(Now.px,Now.py);               if( flag )               {                 if( !Walk[Next.x][Next.y][Next.px][Next.py] )                 {                     Q[tail++]=Next;                     Walk[Next.x][Next.y][Next.px][Next.py]=1;                 }                 if( Map[Next.x][Next.y]==3 )                 {                     printf("%d\n",Next.step);                     return;                 }               }       }   }   printf("-1\n");}int main(){    //freopen("in.txt","r",stdin);    int t;    scanf("%d",&t);    while( t-- )    {        scanf("%d%d",&m,&n);        for( int i=1; i<=m; ++i )        {            for( int j=1; j<=n; ++j )            {                scanf("%d",&Map[i][j]);                if( Map[i][j]==2 )                {                    sx1=i;                    sy1=j;                }                else if( Map[i][j]==4 )                {                    spx=i;                    spy=j;                }            }        }        memset(Walk,0,sizeof(Walk));        Walk[sx1][sy1][spx][spy]=1;        BFS();    }    return 0;}