round_robbin.c

#include <stdio.h>
void sort(int pid[], int at[], int bt[], int n) {
    int temp, i, j, flag;
    for(i = 1;i<n;i++) {
	flag = 1;
	for(j = 0;j<(n-i);j++) {
	    if(at[j]>at[j + 1]) {
		temp = pid[j];
		pid[j] = pid[j + 1];
		pid[j + 1] = temp;
		temp = at[j];
		at[j] = at[j + 1];
		at[j + 1] = temp;
		temp = bt[j];
		bt[j] = bt[j + 1];
		bt[j + 1] = temp;
		flag = 0;
	    }
	}
	if(flag) {
	    break;
	}
    }
}
void display(int pid[], int at[], int bt[], int ct[], int tat[], int wt[], int n) {
    int i;
    float avg_tat, avg_wt;
    puts("\nPID\tAT\tBT\tCT\tTAT\tWT");
    for(i = 0;i<n;i++) {
	printf("%d\t%d\t%d\t%d\t%d\t%d\n", pid[i], at[i], bt[i], ct[i], tat[i], wt[i]);
	avg_tat += tat[i];
	avg_wt += wt[i];
    }
    printf("Average waiting time - %.2f\n", avg_wt/n);
    printf("Average turn around time - %.2f", avg_tat/n);
}
void calc(int pid[], int at[], int bt[], int quantum, int n) {
    int cur_pindex = 0, i, bt_copy[n], elap, queue[50], front = -1, rear = -1;
    int ct[n], tat[n], wt[n];
    sort(pid, at, bt, n);
    for(i = 0;i<n;bt_copy[i] = bt[i], i++);
    elap = at[cur_pindex];
    i = 1;
    printf("Gantt chart - ");
    do {
	printf("%d, ", pid[cur_pindex]);
	if(bt_copy[cur_pindex]>quantum) {
	    elap += quantum;
	    bt_copy[cur_pindex] -= quantum;
	}
	else {
	    elap += bt_copy[cur_pindex];
	    bt_copy[cur_pindex] = 0;
	    ct[cur_pindex] = elap;
	    tat[cur_pindex] = ct[cur_pindex] - at[cur_pindex];
	    wt[cur_pindex] = tat[cur_pindex] - bt[cur_pindex];
	}
	for(;at[i] <= elap && i<n;i++) {
	    queue[++rear] = i;
	}
	if(bt_copy[cur_pindex] != 0) {
	    queue[++rear] = cur_pindex;
	}
	cur_pindex = queue[++front];
    }
    while(front <= rear);
    display(pid, at, bt, ct, tat, wt, n);
}

int main() {
    int at[] = {5, 4, 3, 1, 2, 6};
    int bt[] = {5, 6, 7, 9, 2, 3};
    int pid[] = {1, 2, 3, 4, 5, 6};
    int quantum = 3, n = 6;
    calc(pid, at, bt, quantum, n);
}