#include <iostream>#include <string.h>#include <stdio.h>using namespace std;char mg[120][120];int n,m;int tx,ty,sx,sy;int dx[] = {-1,0,1,0};int dy[] = {0,1,0,-1};bool dir[120][120][4];bool vis[120][120];bool ans;struct point{ int x,y;};point pp[10000];bool isok(int x,int y){ if(x>=0&&x<=n+1&&y>=0&&y<=m+1) return true; else return false;}bool isok2(int x,int y){ if(x>=1&&x<=n&&y>=1&&y<=m) return true; else return false;}bool istrue(int x,int y){ if(isok2(x+1,y+1)&&mg[x+1][y]=='.'&&mg[x+1][y+1]=='.'&&mg[x][y+1]=='.') return true; if(isok2(x-1,y-1)&&mg[x-1][y]=='.'&&mg[x-1][y-1]=='.'&&mg[x][y-1]=='.') return true; if(isok2(x-1,y+1)&&mg[x-1][y]=='.'&&mg[x-1][y+1]=='.'&&mg[x][y+1]=='.') return true; if(isok2(x+1,y-1)&&mg[x][y-1]=='.'&&mg[x+1][y-1]=='.'&&mg[x+1][y]=='.') return true; return false;}void bfs(){ int front = 0,rear = 0; point st; st.x = 0,st.y = 0; vis[0][0] = true; mg[st.x][st.y] = '*'; pp[rear++] = st; point tp; while(front<rear){ tp = pp[front++]; if((mg[tp.x-1][tp.y]=='#'&&mg[tp.x+1][tp.y]=='#')||(mg[tp.x][tp.y-1]=='#'&&mg[tp.x][tp.y+1]=='#')){ sx = tp.x;sy = tp.y; return ; } mg[tp.x][tp.y] = '*'; for(int i=0;i<4;++i){ int xx = tp.x+dx[i]; int yy = tp.y+dy[i]; if(isok(xx,yy)){ if(!vis[xx][yy]&&mg[xx][yy] == '.'){ point temp; temp.x = xx;temp.y = yy; vis[xx][yy] = true; pp[rear++] = temp; } } } }}void dfs(int x,int y,int d){ if(ans == true) return ; if(istrue(x,y)){ ans = true; } else{ for(int i=3;i<=6;++i){ int td = (d+i)%4; if(isok2(x+dx[td],y+dy[td])&&dir[x][y][td] == false&&mg[x+dx[td]][y+dy[td]]=='.'){ dir[x][y][td] = true; dfs(x+dx[td],y+dy[td],td); break; } } }}int main(){ while(scanf("%d%d",&n,&m)!=EOF){ memset(vis,false,sizeof(vis)); memset(mg,'.',sizeof(mg)); getchar(); for(int i=1;i<=n;++i){ for(int j=1;j<=m;++j){ scanf("%c",&mg[i][j]); } getchar(); } bfs(); for(int i=0;i<=n;++i){ for(int j=0;j<=m;++j){ if(mg[i][j] == '*') mg[i][j] = '#'; } } memset(dir,false,sizeof(dir)); ans = false; dfs(sx,sy,0); if(ans) printf("YESn"); else printf("NOn"); } return 0;}
