BFS/poj 2251 Dungeon Master

#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;

const int dx[6]={1,0,-1,0,0,0};
const int dy[6]={0,1,0,-1,0,0};
const int dz[6]={0,0,0,0,1,-1};

struct point
{
    int x,y,z;
    int step;
};

int L,R,C,ex,ey,ez,sx,sy,sz;
char a[30][30][30];
bool v[30][30][30];

bool pd(int x,int y,int z)
{
    if (x>=0 && x<C && y>=0 && y<R && z>=0 && z<L && a[z][y][x]!='#' && v[x][y][z]==0) return true;
    return false;
}

int bfs(int sx,int sy,int sz,int ex,int ey,int ez)
{
    memset(v,0,sizeof(v));
    queue<point>que;
    point now;
    now.x=sx;now.y=sy;now.z=sz;
    now.step=0;
    v[sx][sy][sz]=1;
    que.push(now);
    point next;
    while (!que.empty())
    {
        now=que.front();
        que.pop();
        if (now.x==ex && now.y==ey && now.z==ez) break;
        for (int i=0;i<6;i++)
        {
            next.x=now.x+dx[i];
            next.y=now.y+dy[i];
            next.z=now.z+dz[i];
            if (pd(next.x,next.y,next.z))
            {
                v[next.x][next.y][next.z]=1;
                next.step=now.step+1;
                que.push(next);
            }
        }

    }
    return now.step;
}

int main()
{
    scanf("%d%d%d",&L,&R,&C);
    while (L!=0)
    {
        for (int z=0;z<L;z++)
        {
            for (int y=0;y<R;y++)
            {
                scanf("%s",a[z][y]);
                for (int x=0;x<C;x++)
                {
                    if (a[z][y][x]=='S'){sx=x;sy=y;sz=z;}
                    else if (a[z][y][x]=='E'){ex=x;ey=y;ez=z;}
                }
            }
        }
        int ans=bfs(sx,sy,sz,ex,ey,ez);
        if (ans==0) printf("Trapped!\n");
        else printf("Escaped in %d minute(s).\n",ans);
        scanf("%d%d%d",&L,&R,&C);
    }
    return 0;
}