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# Implementation of First Come First Served scheduling algorithm

# In this Algorithm we just care about the order that the processes arrived

# without carring about their duration time

# https://en.wikipedia.org/wiki/Scheduling_(computing)#First_come,_first_served

from typing import List

def calculate_waiting_times(duration_times: List[int]) -> List[int]:

"""

This function calculates the waiting time of some processes that have a

specified duration time.

Return: The waiting time for each process.

>>> calculate_waiting_times([5, 10, 15])

[0, 5, 15]

>>> calculate_waiting_times([1, 2, 3, 4, 5])

[0, 1, 3, 6, 10]

>>> calculate_waiting_times([10, 3])

[0, 10]

"""

waiting_times = [0] * len(duration_times)

for i in range(1, len(duration_times)):

waiting_times[i] = duration_times[i - 1] + waiting_times[i - 1]

return waiting_times

def calculate_turnaround_times(

duration_times: List[int], waiting_times: List[int]

) -> List[int]:

"""

This function calculates the turnaround time of some processes.

Return: The time difference between the completion time and the

arrival time.

Practically waiting_time + duration_time

>>> calculate_turnaround_times([5, 10, 15], [0, 5, 15])

[5, 15, 30]

>>> calculate_turnaround_times([1, 2, 3, 4, 5], [0, 1, 3, 6, 10])

[1, 3, 6, 10, 15]

>>> calculate_turnaround_times([10, 3], [0, 10])

[10, 13]

"""

return [

duration_time + waiting_times[i]

for i, duration_time in enumerate(duration_times)

]

def calculate_average_turnaround_time(turnaround_times: List[int]) -> float:

"""

This function calculates the average of the turnaround times

Return: The average of the turnaround times.

>>> calculate_average_turnaround_time([0, 5, 16])

7.0

>>> calculate_average_turnaround_time([1, 5, 8, 12])

6.5

>>> calculate_average_turnaround_time([10, 24])

17.0

"""

return sum(turnaround_times) / len(turnaround_times)

def calculate_average_waiting_time(waiting_times: List[int]) -> float:

"""

This function calculates the average of the waiting times

Return: The average of the waiting times.

>>> calculate_average_waiting_time([0, 5, 16])

7.0

>>> calculate_average_waiting_time([1, 5, 8, 12])

6.5

>>> calculate_average_waiting_time([10, 24])

17.0

"""

return sum(waiting_times) / len(waiting_times)

if __name__ == "__main__":

# process id's

processes = [1, 2, 3]

# ensure that we actually have processes

if len(processes) == 0:

print("Zero amount of processes")

exit()

# duration time of all processes

duration_times = [19, 8, 9]

# ensure we can match each id to a duration time

if len(duration_times) != len(processes):

print("Unable to match all id's with their duration time")

exit()

# get the waiting times and the turnaround times

waiting_times = calculate_waiting_times(duration_times)

turnaround_times = calculate_turnaround_times(duration_times, waiting_times)

# get the average times

average_waiting_time = calculate_average_waiting_time(waiting_times)

average_turnaround_time = calculate_average_turnaround_time(turnaround_times)

# print all the results

print("Process ID\tDuration Time\tWaiting Time\tTurnaround Time")

for i, process in enumerate(processes):

print(

f"{process}\t\t{duration_times[i]}\t\t{waiting_times[i]}\t\t"

f"{turnaround_times[i]}"

)

print(f"Average waiting time = {average_waiting_time}")

print(f"Average turn around time = {average_turnaround_time}")

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