(UVA) A Node Too Far - Solução

If you want to see another solution for this problem, click here.

Comparing the run time between the solutions:
- The oldest solution ran in: 1.742s.
- This new solution ran in: 0.655s.

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

class Main  {
    public static HashMap<Integer, ArrayList<Integer>> adjList = new HashMap<Integer, ArrayList<Integer>>();
   
    public static int bfs(int start, int ttl) {
        Queue<Element> queue = new ArrayDeque<Element>();
        Element e = new Element(start, 0);
        queue.add(e);
       
        HashSet<Integer> addedToQueue = new HashSet<Integer>();
        addedToQueue.add(start);

        int reach = 0;
        while (queue.size() > 0 && queue.element().distance <= ttl) {
            int currNode = queue.element().node;
           
            ArrayList<Integer> neighbors = adjList.get(currNode);
            for (int i = 0; i < neighbors.size(); i++) {
                if (!addedToQueue.contains(neighbors.get(i))) {
                    e = new Element(neighbors.get(i), queue.element().distance+1);
                    queue.add(e);
                    addedToQueue.add(neighbors.get(i));
                }           
            }
           
            reach++;
            queue.remove();
        }
       
        return reach;
    }
   
    public static void checkAdjList(int node1, int node2) {
        if (!adjList.containsKey(node1)) {
            ArrayList<Integer> list = new ArrayList<Integer>();
            adjList.put(node1, list);
        }
        adjList.get(node1).add(node2);
    }
   
    public static void readConnections(Scanner sc, int numConnections) {
        for (int i = 0; i < numConnections; i++) {
            int a = sc.nextInt();
            int b = sc.nextInt();
           
            checkAdjList(a, b);
            checkAdjList(b, a);
        }
    }
   
    public static void process() throws NumberFormatException, IOException {   
        Scanner sc = new Scanner(System.in);
       
        int count = 0;
        int numConnections = sc.nextInt();
       
        while (numConnections != 0) {
            readConnections(sc, numConnections);
           
            int start = sc.nextInt();
            int ttl = sc.nextInt();
            while (start != 0 || ttl != 0) {
                System.out.println("Case " + ++count + ": " + (adjList.size()-bfs(start, ttl)) + " nodes not reachable from node " + start + " with TTL = " + ttl + ".");
               
                start = sc.nextInt();
                ttl = sc.nextInt();
            }
           
            adjList.clear();
            numConnections = sc.nextInt();           
        }
       
        return;
    }
   
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();

        System.exit(0);
    }
}

class Element {
    int node;
    int distance;
   
    public Element(int node, int distance) {
        this.node = node;
        this.distance = distance;
    }
}