Breadth First Search: Shortest Reach

Breadth_First_Search_Shortest_Reach.java

import java.io.*;
import java.util.*;

public class Solution {
    public static void main(String[] args) throws FileNotFoundException {
        Scanner in = new Scanner(System.in);
        int t = in.nextInt();
        for (int i = 0; i < t; i++) {
            int n = in.nextInt();
            int m = in.nextInt();
            int from, to;
            HashMap<Integer, Set<Integer>> map = new HashMap<>();
            for (int j = 0; j < m; j++) {
                from = in.nextInt();
//                System.out.println("from : " + from);
                to = in.nextInt();
//                System.out.println("to : " + to);
                if (map.containsKey(from)) {
                    Set<Integer> list = map.get(from);
                    list.add(to);
                    map.put(from, list);
                } else {
                    map.put(from, new HashSet<Integer>(Arrays.asList(to)));
                }
                
                if (map.containsKey(to)) {
                	Set<Integer> list = map.get(to);
                    list.add(from);
                    map.put(to, list);
                } else {
                    map.put(to, new HashSet<Integer>(Arrays.asList(from)));
                }
            }
            int s = in.nextInt();
            printShortest(s, n, map);
        }
        in.close();
    }
    
    private static void printShortest(int s, int n, Map<Integer, Set<Integer>> map) {
        int [] distance = new int [n];
        HashSet<Integer> visited = new HashSet<>();
        Queue<Integer> q = new LinkedList<>();
        q.add(s);
        while (!q.isEmpty()) {
            int v = q.remove();
            if (visited.contains(v)) {
                continue;
            } else {
                visited.add(v);
                
                Set<Integer> set = map.get(v);
                if (set != null) {
                	q.addAll(set);
                    for (Integer i : set) {
                    	if (distance [i - 1] == 0)
                    		distance[i - 1] = distance[v - 1] + 6;
                    }	
                }
            }            
        }
        
        for (int i = 0; i < n; i++) {
            if (i == s - 1) {
                continue;
            } else {
                if (distance[i] == 0) {
                    System.out.print(-1);
                } else {
                    System.out.print(distance[i]);
                }
            }
            System.out.print(i == n - 1? "\n" : ' ');            
        }
    }
}