kill-process.py

# -*- coding: utf-8 -*-
"""
Created on Sat Feb 15 12:48:40 2020

@author: johnoyegbite
"""
# SOLVED
"""
Problem:
    In this problem, each process has a unique PID (process id) and
    PPID (parent process id).

    Each process only has one parent process, but may have one or more
    children processes.
    This is just like a tree structure. Only one process has PPID that is 0,
    which means this process has no parent process. All the PIDs will be
    distinct positive integers.

    We use two list of integers to represent a list of processes, where the
    first list contains PID for each process and the second list contains the
    corresponding PPID.

    Now given the two lists, and a PID representing a process you want to kill,
    return a list of PIDs of processes that will be killed in the end.
    You should assume that when a process is killed, all its children processes
    will be killed. No order is required for the final answer.


Example 1:
    Input: PID = [1, 3, 10, 5], PPID = [3, 0, 5, 3], killID = 5
    Output: [5, 10]
    Explanation: Kill 5 will also kill 10.
         3
       /   \
      1     5
           /
          10

Example 2:
    Input: PID = [1, 2, 3], PPID = [0, 1, 1], killID = 2
    Output: [2]
    Notice:
        The given kill id is guaranteed to be one of the given PIDs.
        There is at least one PID in the list.
"""


def killProcess(pid, ppid, kill):
    # Write your code here

    parent_nodes = {}
    for idx, parent in enumerate(ppid):
        if parent > 0:
            children = parent_nodes.get(parent, [])
            children.append(pid[idx])
            parent_nodes[parent] = children

    i = 0
    queue = [kill]
    pid_killed = []
    while i < len(queue):
        node = queue[i]
        pid_killed.append(node)
        if node in parent_nodes:
            children = parent_nodes[node]
            for child in children:
                queue.append(child)
        i += 1
    return pid_killed


if __name__ == "__main__":
    pid = [1, 3, 10, 5]
    ppid = [3, 0, 5, 3]
    kill = 5
    print(killProcess(pid, ppid, kill))