Added first come first served scheduling (TheAlgorithms#1722)

* Added FCFS

* Fixed spelling error

* Rename fcfs.py to first_come_first_served.py

* Fixed FCFS and added tests.

* Made changes requested

* Use enumerate() instead of range(len())

Co-authored-by: Christian Clauss <[email protected]>

Author: Ale3androsS

scheduling/first_come_first_served.py

@@ -0,0 +1,104 @@
+# 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{turnaround_times[i]}"
+        )
+    print(f"Average waiting time = {average_waiting_time}")
+    print(f"Average turn around time = {average_turnaround_time}")