bfs from hacker rank (bsp)

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.stream.IntStream;

public class Solution {

  public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
   Scanner scanner = new Scanner(System.in);
    int myInt = scanner.nextInt();
    char[][] matrix =new char[myInt][myInt];
    for(int i=0;i<myInt;i++) {
      String myString = scanner.next();
      int k=i;
      IntStream.range(0,myString.length())
          .forEach(c -> matrix[k][c]=myString.charAt(c));
    }
    scanner.close();



   displayPathtoPrincess(myInt, matrix);
   
  }

  static void  displayPathtoPrincess(int n,char[][] grid)
  {
    // initial
    PathStep step = new PathStep((n-1)/2,(n-1)/2 , null,null);
    LinkedList<PathStep> queue = new LinkedList<>();
    queue.add(step);
    // using set to check if already traversed
    HashSet<Integer> set = new HashSet<>();
    boolean findDest = false;
    while(!queue.isEmpty() && !findDest) {
      LinkedList<PathStep> tmpQueue = new LinkedList<>();
      while(!queue.isEmpty()) {
        step = queue.remove();
        int i = step.i, j = step.j, id;
        if(grid[i][j] == 'p') {	// find dest
          findDest = true;
          break;
        }
        PathStep next;
        // move left
        if(j > 0 ) {
          id = n * i + (j - 1);
          if(!set.contains(id)) {
            set.add(id);
            next = new PathStep(i, j - 1, step,"LEFT");
            tmpQueue.add(next);
          }
        }
        // move right
        if(j < n - 1) {
          id = n * i + (j + 1);
          if(!set.contains(id)) {
            set.add(id);
            next = new PathStep(i, j + 1, step,"RIGHT");
            tmpQueue.add(next);
          }
        }
        // move up
        if(i > 0) {
          id = n * (i - 1) + j;
          if(!set.contains(id)) {
            set.add(id);
            next = new PathStep(i - 1, j, step,"UP");
            tmpQueue.add(next);
          }
        }
        // move down
        if(i < n - 1) {
          id = n * (i + 1) + j;
          if(!set.contains(id)) {
            set.add(id);
            next = new PathStep(i + 1, j, step,"DOWN");
            tmpQueue.add(next);
          }
        }
      }
      queue = tmpQueue;

    }
    if(findDest) {
      // build path
      ArrayList<PathStep> path = new ArrayList<>();
      while(step != null) {
        path.add(step);
        step = step.prev;
      }
      Collections.reverse(path);
      // print path
      for(int i = 1; i < path.size(); i++) {
          System.out.println(path.get(i));
      }
    }
  }

  static class PathStep {
    int i, j;
    PathStep prev;
    String direction;

    public PathStep(int i, int j, PathStep prev,String direction) {
      this.i = i;
      this.j = j;
      this.prev = prev;
      this.direction=direction;
    }

    public String toString() {
      return direction;
    }
  }

}