poj 1376 Robot BFS

简单的BFS：

题意：一个机器人从起点到终点有的时间，其中按几种命令走，命令有：向左或向右转，向前走时可以走｛1，2，3｝三种步骤走每次命令消耗1秒，其中如图，机器人在每格的左上角；

想法：这个题最关键是如何保存图按图将横竖都扩大一，保存每个方格的四个定点：若Map[i][j]==1则Map[i][j-1]=1; Map[i-1][j]=1; Map[i-1][j-1]=1;（由于机器人有直径则不可到达边界点）；

代码实现：

#include <iostream>#include <cstring>#include <cstdio>#include <queue>using namespace std;const int MAX=56;int Move[4][2]={{-1,0},{0,1},{1,0},{0,-1}};//N,E,S,Wint Map[MAX][MAX],n,m;bool Visted[MAX][MAX][4];int pre[MAX*MAX*MAX];struct Node{    int x,y,dir;    int time;};queue<Node> Q;void BFS( int x1, int y1, int x2, int y2, int dir ){    if( x1==x2 && y1==y2 )    {        printf("0\n");        return;    }    while( !Q.empty() )      Q.pop();    memset(Visted,0,sizeof(Visted));    Visted[x1][y1][dir]=1;    Node p1;    p1.x=x1;    p1.y=y1;    p1.time=0;    p1.dir=dir;    Q.push(p1);    while( !Q.empty() )    {        Node Now;        Now=Q.front();        if( Now.x==x2 && Now.y==y2 )        {            printf("%d\n",Now.time);            return;        }        Q.pop();        for( int i=1; i<=3; ++i )        {            Node Next;            Next.x=Now.x+Move[Now.dir][0]*i;            Next.y=Now.y+Move[Now.dir][1]*i;            Next.dir=Now.dir;            Next.time=Now.time+1;            if( Next.x<=0 || Next.y<=0 || Next.x>=n || Next.y>=m || Map[Next.x][Next.y] )                break;            if( !Visted[Next.x][Next.y][Next.dir] && Map[Next.x][Next.y]==0 )            {                Visted[Next.x][Next.y][Next.dir]=1;                Q.push(Next);            }        }        Node Next;        Next.x=Now.x;        Next.y=Now.y;        Next.dir=(Now.dir+3)%4;        Next.time=Now.time+1;        if( !Visted[Next.x][Next.y][Next.dir] )        {            Visted[Next.x][Next.y][Next.dir]=1;            Q.push(Next);        }        Next.dir=(Now.dir+1)%4;        if( !Visted[Next.x][Next.y][Next.dir] )        {            Visted[Next.x][Next.y][Next.dir]=1;            Q.push(Next);        }    }    printf("-1\n");}int main(){    //freopen("in.txt","r",stdin);   // freopen("out.txt","w",stdout);    int x1,y1,x2,y2;    char Dir[10];    while( scanf("%d%d",&n,&m)!=EOF )    {        if( !n && !m )          break;        memset(Map,0,sizeof(Map));        for( int i=1; i<=n; i++ )         for( int j=1; j<=m; j++ )         {             scanf("%d",&Map[i][j]);             if( Map[i][j]==1 )             {                 Map[i][j-1]=1;                 Map[i-1][j]=1;                 Map[i-1][j-1]=1;             }         }       scanf("%d%d%d%d",&x1,&y1,&x2,&y2);       getchar();       scanf("%s",Dir);       int k=-1;       if( Dir[0]=='n' )         k=0;       else if( Dir[0]=='e' )        k=1;       else if( Dir[0]=='s' )        k=2;       else         k=3;       BFS(x1,y1,x2,y2,k);    }    return 0;}