Question

Assuming you are write a program for the emergency room. You maintain two queues. A regular FIFO queue for doctors. When a doctor walked in, he/she will join this queue if there is no patients waiting.
Otherwise, remove the patient with the highest priority and let the doctor treat this patient.
A priority queue for patients. When a patient walked, input patients name and priority. If doctor’s queue is not empty, remove the first doctor and let this doctor server this patients. Otherwise add this patient with the priority to the priority queue.
PYTHON

Answer 1

Code tested in Python 3.6.9 in the Linux operating system.

Idea

We will use 2 modules available in Python to solve this problem

1. deque: deque is short for "double-ended queue". It supports add and remove operations at both front and back. It can be used to implement a stack or a queue. We'll use it to implement the doctors queue.
2. heapq: heapq provides us the implementation of a priority queue that we can use to add patients or remove patients.

Helpful and self-explanatory comments are added to the code and output is also attached.

Code

from collections import deque
from heapq import heappush, heappop

class Doctor:
  def __init__(self, id):
    self.id = id

class Patient:
  def __init__(self, name, priority):
    self.name = name
    self.priority = priority
  # Comparator method for priority queue
  def __lt__(self, other):
    if self.priority == other.priority:
      # If priority is same, take element with lexographically shorter name first
      return self.name <= other.name
    # Else, take element with higher priorty first
    return self.priority > other.priority

doctors_queue = deque()
waiting_list = [] # For patients

# Series of events
events = [
  Patient('John', 10), # (Patient Name, Priority)
  Patient('Wick', 20),
  Doctor(1), # (DoctorID)
  Doctor(2),
  Doctor(3),
  Doctor(4),
  Patient('Lorem', 2),
  Patient('Epsum', 1),
  Patient('EFD', 1),
  Patient('ABC', 1),
  Doctor(5),
]

# Process events
for e in events:
  # Check if a doctor arrived
  if isinstance(e, Doctor):
    print('Doctor {} arrived'.format(e.id))
    # Check if a patient is waiting
    if len(waiting_list) > 0:
      # Pop the highest priority patient from waiting list
      patient = heappop(waiting_list)
      print('Patient [{}] with priority = {} assigned to Doctor {}'.format(patient.name, patient.priority, e.id))
    else:
      # No patient waiting, join the queue
      doctors_queue.append(e)
      print('Doctor {} joined the queue'.format(e.id))
  else:
    print('Patient [{}] with priority = {} arrived'.format(e.name, e.priority))
    # Check if a doctor is available
    if len(doctors_queue) > 0:
      # If yes, assign patient to this doctor
      doctor = doctors_queue.popleft()
      print('Patient [{}] with priority = {} assigned to Doctor {}'.format(e.name, e.priority, doctor.id))
    else:
      # Otherwise, add patient to priority queue
      heappush(waiting_list, e)
      print('Patient [{}] joined the queue'.format(e.name))

Output