description: Monocarp is playing a computer game. Now he wants to complete the first level of this game.
  
  A level is a rectangular grid of 2 rows and n columns. Monocarp controls a character, which starts in cell (1, 1) — at the intersection of the 1-st row and the 1-st column.
  
  Monocarp's character can move from one cell to another in one step if the cells are adjacent by side and/or corner. Formally, it is possible to move from cell (x_1, y_1) to cell (x_2, y_2) in one step if |x_1 - x_2| ≤ 1 and |y_1 - y_2| ≤ 1. Obviously, it is prohibited to go outside the grid.
  
  There are traps in some cells. If Monocarp's character finds himself in such a cell, he dies, and the game ends.
  
  To complete a level, Monocarp's character should reach cell (2, n) — at the intersection of row 2 and column n.
  
  Help Monocarp determine if it is possible to complete the level.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 100) — the number of test cases. Then the test cases follow. Each test case consists of three lines.
  
  The first line contains a single integer n (3 ≤ n ≤ 100) — the number of columns.
  
  The next two lines describe the level. The i-th of these lines describes the i-th line of the level — the line consists of the characters '0' and '1'. The character '0' corresponds to a safe cell, the character '1' corresponds to a trap cell.
  
  Additional constraint on the input: cells (1, 1) and (2, n) are safe.
  
  Output
  
  For each test case, output YES if it is possible to complete the level, and NO otherwise.
  
  Example
  
  Input
  
  
  4
  3
  000
  000
  4
  0011
  1100
  4
  0111
  1110
  6
  010101
  101010
  
  
  Output
  
  
  YES
  YES
  NO
  YES
  
  Note
  
  Consider the example from the statement.
  
  In the first test case, one of the possible paths is (1, 1) → (2, 2) → (2, 3).
  
  In the second test case, one of the possible paths is (1, 1) → (1, 2) → (2, 3) → (2, 4).
  
  In the fourth test case, one of the possible paths is (1, 1) → (2, 2) → (1, 3) → (2, 4) → (1, 5) → (2, 6).
solution: import java.util.*;
  public class Main{
      public static boolean issafe(int n,int i,int j,int[][] grid){
          if(i<0 || j<0 || i>=2 || j>=n || grid[i][j]!=0){
              return false;
          }
          return true;
      }
      public static boolean dfs(int i,int j,int n,int[][] grid){
          int []rowstep={0,1,1,-1,-1};
          int []colstep={1,0,1,0,1};
          if(issafe(n,i,j,grid)){
              if(j==n-1){
                  return true;
              }
              grid[i][j]=1;
              for(int k=0;k<5;k++){
                  int x=i+rowstep[k];
                  int y=j+colstep[k];
                  if(dfs(x,y,n,grid)){
                      return true;
                  }
              }
          }
          return false;
      }
      public static void main(String[] args){
          Scanner sc=new Scanner(System.in);
          int t=sc.nextInt();
          while(t-->0){
              int n=sc.nextInt();
              int[][] grid=new int[2][n];
              sc.nextLine();
              String a=sc.nextLine();
              String b=sc.nextLine();
              for(int i=0;i<2;i++){
                  for(int j=0;j<n;j++){
                      if(i==0)
                          grid[i][j]=Integer.parseInt(a.charAt(j)+"");
                      else
                          grid[i][j]=Integer.parseInt(b.charAt(j)+"");
                  }
              }
              if(dfs(0,0,n,grid)){
                  System.out.println("YES");
              }
              else{
                  System.out.println("NO");
              }
          }
      }
  }