'''
SJF: Shortest Job First
The task is to find the Average Waiting Time and Average Turnaround Time of the given processes with their Burst Time using SJF Scheduling Algorithm.
SJF is a scheduling policy that selects the waiting process with the smallest execution time to execute next.
SJF is a Non Pre-emptive Algorithm, hence the process which has the least Burst Time will be served first and the next process will be served only after the previous process is executed completely.
SJF has the advantage of having a minimum average waiting time among all scheduling algorithms.
Here we are considering the arrival time of all processes to be 0.
Start Time: Time at which the execution of the process starts
Completion Time: Time at which the process completes its execution
Turnaround Time: Completion Time - Arrival Time
Waiting Time: Turnaround Time - Burst Time
'''


class SJF:

    def processData(self, no_of_processes):
        process_data = []
        for i in range(no_of_processes):
            temporary = []
            process_id = int(input("Enter Process ID: "))

            burst_time = int(input(f"Enter Burst Time for Process {process_id}: "))

            temporary.extend([process_id, 0, burst_time])
            '''
            '0' is the arrival time of the processes
            '''
            process_data.append(temporary)
        SJF.schedulingProcess(self, process_data)

    def schedulingProcess(self, process_data):
        process_data.sort(key=lambda x: x[2])

        '''

        Sort according to Burst Time 
        '''

        start_time = []
        exit_time = []
        s_time = 0
        for i in range(len(process_data)):
            start_time.append(s_time)
            s_time = s_time + process_data[i][2]
            e_time = s_time
            exit_time.append(e_time)
            process_data[i].append(e_time)
        t_time = SJF.calculateTurnaroundTime(self, process_data)
        w_time = SJF.calculateWaitingTime(self, process_data)
        SJF.printData(self, process_data, t_time, w_time)

    def calculateTurnaroundTime(self, process_data):
        total_turnaround_time = 0
        for i in range(len(process_data)):
            turnaround_time = process_data[i][3] - process_data[i][1]
            '''
            turnaround_time = completion_time - arrival_time
            '''
            total_turnaround_time = total_turnaround_time + turnaround_time
            process_data[i].append(turnaround_time)
        average_turnaround_time = total_turnaround_time / len(process_data)
        '''
        average_turnaround_time = total_turnaround_time / no_of_processes
        '''
        return average_turnaround_time

    def calculateWaitingTime(self, process_data):
        total_waiting_time = 0
        for i in range(len(process_data)):
            waiting_time = process_data[i][4] - process_data[i][2]
            '''
            waiting_time = turnaround_time - burst_time
            '''
            total_waiting_time = total_waiting_time + waiting_time
            process_data[i].append(waiting_time)
        average_waiting_time = total_waiting_time / len(process_data)
        '''
        average_waiting_time = total_waiting_time / no_of_processes
        '''
        return average_waiting_time

    def printData(self, process_data, average_turnaround_time, average_waiting_time):

        print("Process_ID  Arrival_Time  Burst_Time  Completion_Time  Turnaround_Time  Waiting_Time")

        for i in range(len(process_data)):
            for j in range(len(process_data[i])):
                print(process_data[i][j], end="				")
            print()

        print(f'Average Turnaround Time: {average_turnaround_time}')

        print(f'Average Waiting Time: {average_waiting_time}')


if __name__ == "__main__":

    no_of_processes = int(input("Enter number of processes: "))
    sjf = SJF()
    sjf.processData(no_of_processes)

Output: