Find_All_People_With_Secret.java

import java.util.*;
import java.io.*;
import java.lang.*;
public class Find_All_People_With_Secret {
    class Solution {
        public List<Integer> findAllPeople(int n, int[][] meetings, int firstPerson) {

            Map<Integer, List<int[]>> graph = new HashMap<>();
            for (int[] meeting : meetings) {
                int x = meeting[0], y = meeting[1], t = meeting[2];
                graph.computeIfAbsent(x, k -> new ArrayList<>()).add(new int[]{t, y});
                graph.computeIfAbsent(y, k -> new ArrayList<>()).add(new int[]{t, x});
            }

            int[] vis = new int[n];
            Arrays.fill(vis, Integer.MAX_VALUE);
            vis[0] = 0;
            vis[firstPerson] = 0;

            Queue<int[]> q = new ArrayDeque<>();
            q.offer(new int[]{0, 0});
            q.offer(new int[]{firstPerson, 0});

            while (!q.isEmpty()) {
                int[] personTime = q.poll();
                int person = personTime[0];
                int time = personTime[1];

                for (int[] nextPersonTime : graph.getOrDefault(person, new ArrayList<>())) {
                    int t = nextPersonTime[0];
                    int nextPerson = nextPersonTime[1];

                    if (t >= time && vis[nextPerson] > t) {
                        vis[nextPerson] = t;
                        q.offer(new int[]{nextPerson, t});
                    }
                }
            }

            List<Integer> al = new ArrayList<>();
            for (int i = 0; i < n; ++i) {
                if (vis[i] != Integer.MAX_VALUE) {
                    al.add(i);
                }
            }
            return al;
        }
    }
}