Solution.java

import java.util.*;

public class Solution
{
    public List<Integer> killProcess(List<Integer> pid, List<Integer> ppid, int kill)
    {
        Map<Integer, List<Integer>> mapping = new HashMap<>();
        for (int i = 0; i < pid.size(); i++)
        {
            int parentProcessId = ppid.get(i);
            mapping.putIfAbsent(parentProcessId, new ArrayList<>());
            mapping.get(parentProcessId).add(pid.get(i));
        }
        List<Integer> killed = new ArrayList<>();
        Queue<Integer> queue = new LinkedList<>();
        queue.add(kill);
        while (!queue.isEmpty())
        {
            int processId = queue.poll();
            killed.add(processId);
            if (mapping.containsKey(processId))
            {
                queue.addAll(mapping.get(processId));
            }
        }
        return killed;
    }
}