Zhangxinrong code:

#include<cstdio>
#include<cstring>
using namespace std;
int n,m;
char s[11000000];
const int dx[]={-1,1,0,0},dy[]={0,0,-1,1},inf=0x3f3f3f3f;
const char dt[]="nswe";
int g[22][22],d[21][21][21][21];
struct point{
	int x,y;
	inline bool operator==(point &b){return x==b.x&&y==b.y;}
}ed;
struct state{point s,b;int dep,pre;char opt;}st,tmp,q[1100000];
int h,t,ans,last;
void bfs(){
	ans=inf;
	h=t=0;q[t++]=st;
	while(h!=t){
		if(q[h].b==ed&&ans>q[h].dep)ans=q[h].dep,last=h;
		for(int i=0;i<4;++i){
			tmp=q[h];
			int x=tmp.s.x,y=tmp.s.y;
			int xx=x+dx[i],yy=y+dy[i];
			int tx=tmp.b.x,ty=tmp.b.y;
			if(g[xx][yy]!=-1){
				if(xx==tx&&yy==ty){//人把箱子撞出一格
					tx+=dx[i],ty+=dy[i];
					if(g[tx][ty]==-1)continue;
					++tmp.dep;
				}
				if(d[xx][yy][tx][ty]>tmp.dep){
					d[xx][yy][tx][ty]=tmp.dep;
					tmp={xx,yy,tx,ty,tmp.dep,h,dt[i]};
					if(tmp.dep!=q[h].dep)tmp.opt-='a'-'A';
					q[t++]=tmp;
				}
			}
		}
		++h;
	}
}
int main(){
	int T=0;
	while(scanf("%d%d",&n,&m)!=EOF&&n&&m){
		memset(d,0x3f,sizeof(d));
		memset(g,-1,sizeof(g));
		for(int i=1;i<=n;++i){
			scanf("%s",s+1);
			for(int j=1;j<=m;++j)
				if(s[j]!='#'){
					g[i][j]=0;
					if(s[j]=='B')st.b={i,j};
					else if(s[j]=='S')st.s={i,j};
					else if(s[j]=='T')ed={i,j};
				}
		}
		printf("Maze #%d\n",++T);
		bfs();
		if(ans==inf){puts("Impossible.\n");continue;}
		int slen=0;
		for(int k=last;k;k=q[k].pre)s[++slen]=q[k].opt;
		for(int i=slen;i>=1;--i)putchar(s[i]);
		puts("\n");
	}
	return 0;
}

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Zhangxinrong code:

#include<cstdio>
#include<cstring>
using namespace std;
int n,m;
char s[11000000];
const int dx[]={-1,1,0,0},dy[]={0,0,-1,1},inf=0x3f3f3f3f;
const char dt[]="nswe";
int g[22][22],d[21][21][21][21];
struct point{
	int x,y;
	inline bool operator==(point &b){return x==b.x&&y==b.y;}
}ed;
struct state{point s,b;int dep,pre;char opt;}st,tmp,q[1100000];
int h,t,ans,last;
void bfs(){
	ans=inf;
	h=t=0;q[t++]=st;
	while(h!=t){
		if(q[h].b==ed&&ans>q[h].dep)ans=q[h].dep,last=h;
		for(int i=0;i<4;++i){
			tmp=q[h];
			int x=tmp.s.x,y=tmp.s.y;
			int xx=x+dx[i],yy=y+dy[i];
			int tx=tmp.b.x,ty=tmp.b.y;
			if(g[xx][yy]!=-1){
				if(xx==tx&&yy==ty){//人把箱子撞出一格
					tx+=dx[i],ty+=dy[i];
					if(g[tx][ty]==-1)continue;
					++tmp.dep;
				}
				if(d[xx][yy][tx][ty]>tmp.dep){
					d[xx][yy][tx][ty]=tmp.dep;
					tmp={xx,yy,tx,ty,tmp.dep,h,dt[i]};
					if(tmp.dep!=q[h].dep)tmp.opt-='a'-'A';
					q[t++]=tmp;
				}
			}
		}
		++h;
	}
}
int main(){
	int T=0;
	while(scanf("%d%d",&n,&m)!=EOF&&n&&m){
		memset(d,0x3f,sizeof(d));
		memset(g,-1,sizeof(g));
		for(int i=1;i<=n;++i){
			scanf("%s",s+1);
			for(int j=1;j<=m;++j)
				if(s[j]!='#'){
					g[i][j]=0;
					if(s[j]=='B')st.b={i,j};
					else if(s[j]=='S')st.s={i,j};
					else if(s[j]=='T')ed={i,j};
				}
		}
		printf("Maze #%d\n",++T);
		bfs();
		if(ans==inf){puts("Impossible.\n");continue;}
		int slen=0;
		for(int k=last;k;k=q[k].pre)s[++slen]=q[k].opt;
		for(int i=slen;i>=1;--i)putchar(s[i]);
		puts("\n");
	}
	return 0;
}