Create non_preemptive_shortest_job_first.py (#6169)

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scheduling/non_preemptive_shortest_job_first.py

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+"""
+Non-preemptive Shortest Job First
+Shortest execution time process is chosen for the next execution.
+https://www.guru99.com/shortest-job-first-sjf-scheduling.html
+https://en.wikipedia.org/wiki/Shortest_job_next
+"""
+
+
+from __future__ import annotations
+
+from statistics import mean
+
+
+def calculate_waitingtime(
+    arrival_time: list[int], burst_time: list[int], no_of_processes: int
+) -> list[int]:
+    """
+    Calculate the waiting time of each processes
+
+    Return: The waiting time for each process.
+    >>> calculate_waitingtime([0,1,2], [10, 5, 8], 3)
+    [0, 9, 13]
+    >>> calculate_waitingtime([1,2,2,4], [4, 6, 3, 1], 4)
+    [0, 7, 4, 1]
+    >>> calculate_waitingtime([0,0,0], [12, 2, 10],3)
+    [12, 0, 2]
+    """
+
+    waiting_time = [0] * no_of_processes
+    remaining_time = [0] * no_of_processes
+
+    # Initialize remaining_time to waiting_time.
+
+    for i in range(no_of_processes):
+        remaining_time[i] = burst_time[i]
+    ready_process: list[int] = []
+
+    completed = 0
+    total_time = 0
+
+    # When processes are not completed,
+    # A process whose arrival time has passed \
+    # and has remaining execution time is put into the ready_process.
+    # The shortest process in the ready_process, target_process is executed.
+
+    while completed != no_of_processes:
+        ready_process = []
+        target_process = -1
+
+        for i in range(no_of_processes):
+            if (arrival_time[i] <= total_time) and (remaining_time[i] > 0):
+                ready_process.append(i)
+
+        if len(ready_process) > 0:
+            target_process = ready_process[0]
+            for i in ready_process:
+                if remaining_time[i] < remaining_time[target_process]:
+                    target_process = i
+            total_time += burst_time[target_process]
+            completed += 1
+            remaining_time[target_process] = 0
+            waiting_time[target_process] = (
+                total_time - arrival_time[target_process] - burst_time[target_process]
+            )
+        else:
+            total_time += 1
+
+    return waiting_time
+
+
+def calculate_turnaroundtime(
+    burst_time: list[int], no_of_processes: int, waiting_time: list[int]
+) -> list[int]:
+    """
+    Calculate the turnaround time of each process.
+
+    Return: The turnaround time for each process.
+    >>> calculate_turnaroundtime([0,1,2], 3, [0, 10, 15])
+    [0, 11, 17]
+    >>> calculate_turnaroundtime([1,2,2,4], 4, [1, 8, 5, 4])
+    [2, 10, 7, 8]
+    >>> calculate_turnaroundtime([0,0,0], 3, [12, 0, 2])
+    [12, 0, 2]
+    """
+
+    turn_around_time = [0] * no_of_processes
+    for i in range(no_of_processes):
+        turn_around_time[i] = burst_time[i] + waiting_time[i]
+    return turn_around_time
+
+
+if __name__ == "__main__":
+    print("[TEST CASE 01]")
+
+    no_of_processes = 4
+    burst_time = [2, 5, 3, 7]
+    arrival_time = [0, 0, 0, 0]
+    waiting_time = calculate_waitingtime(arrival_time, burst_time, no_of_processes)
+    turn_around_time = calculate_turnaroundtime(
+        burst_time, no_of_processes, waiting_time
+    )
+
+    # Printing the Result
+    print("PID\tBurst Time\tArrival Time\tWaiting Time\tTurnaround Time")
+    for i, process_ID in enumerate(list(range(1, 5))):
+        print(
+            f"{process_ID}\t{burst_time[i]}\t\t\t{arrival_time[i]}\t\t\t\t"
+            f"{waiting_time[i]}\t\t\t\t{turn_around_time[i]}"
+        )
+    print(f"\nAverage waiting time = {mean(waiting_time):.5f}")
+    print(f"Average turnaround time = {mean(turn_around_time):.5f}")