DFS

import java.io.*;
import java.util.*;
class Main{
    static int N = 110, row, col;
    static BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
    static char[][] a = new char[N][N];
    static int[][] dir = new int[][]{{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
    public static void main(String[] args) throws Exception{
        int t = Integer.valueOf(read.readLine());
        while(t-- > 0){
            int n = Integer.valueOf(read.readLine());
            row = col = n;
            for(int i = 0; i < n; i++){
                String s = read.readLine();
                for(int j = 0; j < n; j++){
                    a[i][j] = s.charAt(j);
                }
            }
            String[] ss = read.readLine().split(" ");
            int x1 = Integer.valueOf(ss[0]);
            int y1 = Integer.valueOf(ss[1]);
            int x2 = Integer.valueOf(ss[2]);
            int y2 = Integer.valueOf(ss[3]);
            boolean[][] st = new boolean[n][n];
            if(a[x1][y1] == '#' || a[x2][y2] == '#'){
                System.out.println("NO");
            }else if(x1 == x2 && y1 == y2){
                System.out.println("YES");
            }else if(dfs(x1, y1, x2, y2, st)){
                System.out.println("YES");
            }else{
                System.out.println("NO");
            }

        }
    }

    public static boolean dfs(int x1, int y1, int x2, int y2, boolean[][] st){
        for(int i = 0; i < 4; i++){
            int nx = x1 + dir[i][0];
            int ny = y1 + dir[i][1];
            if(nx < 0 || nx >= row || ny < 0 || ny >= col) continue;
            if(st[nx][ny] || a[nx][ny] == '#') continue;
            st[nx][ny] = true;
            if(nx == x2 && ny == y2) return true;
            if(dfs(nx, ny, x2, y2, st)) return true;
        }
        return false;
    }

}

BFS

import java.io.*;
import java.util.*;
class Main{
    static int N = 110, row, col;
    static BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
    static char[][] a = new char[N][N];
    static int[][] dir = new int[][]{{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
    public static void main(String[] args) throws Exception{
        int t = Integer.valueOf(read.readLine());
        while(t-- > 0){
            int n = Integer.valueOf(read.readLine());
            row = col = n;
            for(int i = 0; i < n; i++){
                String s = read.readLine();
                for(int j = 0; j < n; j++){
                    a[i][j] = s.charAt(j);
                }
            }
            String[] ss = read.readLine().split(" ");
            int x1 = Integer.valueOf(ss[0]);
            int y1 = Integer.valueOf(ss[1]);
            int x2 = Integer.valueOf(ss[2]);
            int y2 = Integer.valueOf(ss[3]);
            if(bfs(x1, y1, x2, y2)) System.out.println("YES");
            else System.out.println("NO");
        }
    }

    public static boolean bfs(int x1, int y1, int x2, int y2){
        Queue<int[]> q = new LinkedList();
        if(a[x1][y1] == '#' || a[x2][y2] == '#') return false;
        if(x1 == x2 && y1 == y2)    return true;
        q.offer(new int[]{x1, y1});
        boolean[][] st = new boolean[row][col];
        st[x1][y1] = true;
        while(!q.isEmpty()){
            int[] poll = q.poll();
            for(int i = 0; i < 4; i++){
                int nx = dir[i][0] + poll[0];
                int ny = dir[i][1] + poll[1];
                if(nx < 0 || nx >= row || ny < 0 || ny >= col) continue;
                if(st[nx][ny] || a[nx][ny] == '#') continue;
                st[nx][ny] = true;
                if(nx == x2 && ny == y2) return true;
                q.offer(new int[]{nx, ny});
            }
        }
        return false;
    }
}