> 千万不要在使用了队列pop的时候还引用呀！！我就是这样wa了无数遍。
> 附AC码：
> #include <iostream>
> #include <cstdio>
> #include <queue>
> #include <cstring>
> using namespace std;
> const int MAXN = 50;
> 
> char mp[MAXN][MAXN][MAXN];
> bool vis[MAXN][MAXN][MAXN];
> int l, r, c;
> int dz[]={-1,1,0,0,0,0};
> int dx[]={0,0,0,0,-1,1};
> int dy[]={0,0,-1,1,0,0};
> 
> struct Node{
>     int z, x, y, dis;
>     Node(int a, int b, int c, int d): z(a), x(b), y(c), dis(d){}
> };
> 
> int main() {
>     ios_base::sync_with_stdio(0);
>     while (cin >> l >> r >> c && l + r + c)
>     {
>         int ans = -1;
>         memset(vis, 0, sizeof vis);
>         queue<Node> q;
>         for (int i = 0; i < l; ++i)
>             for (int j = 0; j < r; ++j)
>                 for (int k = 0; k < c; ++k)
>                 {
>                     //cout << i << j << k << endl;
>                     cin >> mp[i][j][k];
>                     if (mp[i][j][k] == 'S')
>                     {
>                         q.push(Node(i, j, k, 0));
>                         vis[i][j][k] = 1;
>                     }
>                 }
>         while (!q.empty())
>         {
>             Node e = q.front(); q.pop();
>             for (int i = 0; i < 6; ++i)
>             {
>                 int nz = e.z + dz[i], nx = e.x + dx[i], ny = e.y + dy[i], ndis = e.dis + 1;
>                 if (0 <= nz && nz < l && 0 <= nx && nx < r && 0 <= ny && ny < c && mp[nz][nx][ny] != '#' && !vis[nz][nx][ny])
>                 {
>                     if (mp[nz][nx][ny] == 'E')
>                         ans = ndis;
>                     vis[nz][nx][ny] = 1;
>                     q.push(Node(nz, nx, ny, ndis));
>                 }
>             }
>         }
>         if (ans == -1)
>             cout << "Trapped!\n";
>         else cout << "Escaped in " << ans << " minute(s).\n";
>     }
>     return 0;
> }