Algorithms/Pre_SJF_Scheduling.java at master · piyush-hack/Algorithms · GitHub

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package java_algo;

import java.util.*;

public class Pre_SJF_Scheduling {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		System.out.println("enter no of process:");
		int n = sc.nextInt();
		int pid[] = new int[n]; // it takes pid of process
		int at[] = new int[n]; // at means arrival time
		int bt[] = new int[n]; // bt means burst time
		int ct[] = new int[n]; // ct means complete time
		int ta[] = new int[n];// ta means turn around time
		int wt[] = new int[n]; // wt means waiting time
		int f[] = new int[n]; // f means it is flag it checks process is completed or not
		int k[] = new int[n]; // it is also stores brust time
		int i, st = 0, tot = 0;
		float avgwt = 0, avgta = 0;

		for (i = 0; i < n; i++) {
			pid[i] = i + 1;
			System.out.println("enter process " + (i + 1) + " arrival time:");
			at[i] = sc.nextInt();
			System.out.println("enter process " + (i + 1) + " burst time:");
			bt[i] = sc.nextInt();
			k[i] = bt[i];
			f[i] = 0;
		}

		while (true) {
			int min = 99, c = n;
			if (tot == n)
				break;

			for (i = 0; i < n; i++) {
				if ((at[i] <= st) && (f[i] == 0) && (bt[i] < min)) {
					min = bt[i];
					c = i;
				}
			}

			if (c == n)
				st++;
			else {
				bt[c]--;
				st++;
				if (bt[c] == 0) {
					ct[c] = st;
					f[c] = 1;
					tot++;
				}
			}
		}

		for (i = 0; i < n; i++) {
			ta[i] = ct[i] - at[i];
			wt[i] = ta[i] - k[i];
			avgwt += wt[i];
			avgta += ta[i];
		}

		System.out.println("pid  arrival  burst  complete turn waiting");
		for (i = 0; i < n; i++) {
			System.out.println(pid[i] + "\t" + at[i] + "\t" + k[i] + "\t" + ct[i] + "\t" + ta[i] + "\t" + wt[i]);
		}

		System.out.println("Gantt Chart : ");

		int temp = 0;
		for (int i1 = 0; i1 < ct.length; i1++) {
			for (int j = i1 + 1; j < ct.length; j++) {
				if (ct[i1] > ct[j]) {
					temp = ct[i1];
					ct[i1] = ct[j];
					ct[j] = temp;

					temp = pid[i1];
					pid[i1] = pid[j];
					pid[j] = temp;

				}
			}
		}

		for (int i1 = 0; i1 <= n; i1++) {
			System.out.print(" ------");
		}

		System.out.println();
		for (int i1 = 0; i1 < n; i1++) {
			System.out.print("|  P" + pid[i1] + "  ");
		}
		System.out.print("|");
		System.out.println();

		System.out.print(0 + "------");
		for (int i1 = 0; i1 < n; i1++) {

			System.out.print(ct[i1] + "-----");

		}

		System.out.println("\naverage tat is " + (float) (avgta / n));
		System.out.println("average wt is " + (float) (avgwt / n));
		sc.close();
	}
}