【poj2157】Maze

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
char map[21][21];
bool vis[21][21],mark[21][21],flag;
const int xx[4]={-1,0,1,0},yy[4]={0,-1,0,1};
int n,m,tot,sx,sy;
struct key{
int tot,sum;
}key[5];
struct door{
int k,x,y;
}door[401];
void dfs(int nowx,int nowy){
mark[nowx][nowy]=true;
if(flag)return;
for(int i=0;i<=3;i++){
int x=nowx+xx[i],y=nowy+yy[i];
if(x<1||y<1||x>n||y>m||map[x][y]=='X'||mark[x][y])continue;
else if(map[x][y]>='a'&&map[x][y]<='e'){
dfs(x,y);
int tmp=map[x][y]-'a';
if(++key[tmp].sum==key[tmp].tot&&key[tmp].sum)
for(int k=1;k<=tot;k++)
if(door[k].k==tmp&&vis[door[k].x][door[k].y])
dfs(door[k].x,door[k].y);
}
else if(map[x][y]>='A'&&map[x][y]<='E'){
vis[x][y]=true;
int tmp=map[x][y]-'A';
if(key[tmp].sum==key[tmp].tot&&key[tmp].sum)
dfs(x,y);
}
else if(map[x][y]=='G')flag=true;
else dfs(x,y);
}
}
void init(){
memset(vis,0,sizeof(vis));
memset(key,0,sizeof(key));
memset(door,0,sizeof(door));
memset(mark,0,sizeof(mark));
tot=flag=0;
}
int main(){
while(scanf("%d%d",&n,&m)&&n){
init();
for(int i=1;i<=n;i++){
scanf("%s",map[i]+1);
for(int j=1;j<=m;j++){
if(map[i][j]=='S'){
sx=i;sy=j;
}
else if(map[i][j]>='a'&&map[i][j]<='e')key[map[i][j]-'a'].tot++;
else if(map[i][j]>='A'&&map[i][j]<='E'){
door[++tot].x=i;door[tot].y=j;door[tot].k=map[i][j]-'A';
}
}
}
dfs(sx,sy);
if(flag)puts("YES");
else puts("NO");
}
return 0;
}