【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;}