Shortest Job First(SJF) Non-preemptive scheduling algorithm by defining process structure.

#include <stdio.h>
#include <stdlib.h>

struct process{
	int pid, at, bt, ct, tt, wt;
};

void main(){
	int n, i;
	printf("No. of Processes>> ");
	scanf("%d",&n);
	struct process p[n];
	
	printf("\nPID\tAT\tBT\n");
	for(i=0;i<n;i++){
		scanf("%d\t%d\t%d",&p[i].pid,&p[i].at,&p[i].bt);
	}
	
	int* isCompleted = (int*)calloc(n,sizeof(int));
	
	int min, index, curtime=0, completed=0, prev=-2, j=0, len=n, tottt=0, totwt=0, pid[20], ct[20];
	
	while(completed!=n){
		index=-1; min=9999;
		for(i=0;i<n;i++){
			if (p[i].at<=curtime && !isCompleted[i]){
				if (min>p[i].bt){
				index = i;
				min = p[i].bt;
				}
			
				if (p[i].bt==min){
					if (p[i].at<p[index].at){
						index = i;
						min = p[i].bt;
					}
				}
			
			}
		}
		
		if (index!=-1){
			p[index].ct = p[index].bt + curtime;
			p[index].tt = p[index].ct - p[index].at;
			p[index].wt = p[index].tt - p[index].bt;
			
			tottt+=p[index].tt;
			totwt+=p[index].wt;
			
			ct[j]=p[index].ct;
			pid[j]=p[index].pid;
			j++;
			
			curtime=p[index].ct;
			completed++;
			isCompleted[index]=1;
		}
		else{
			if (prev=curtime-1){
				ct[j-1]++;
				prev=curtime;
			}
			else{
				pid[j]=-1;
				ct[j]=curtime+1;
				j++;
				len++;
				prev=curtime;
			}
			curtime++;
		}
	}
	
	printf("\nPID\tAT\tBT\tCT\tTT\tWT\n");
	for(i=0;i<n;i++){
		printf("%d\t%d\t%d\t%d\t%d\t%d\n", p[i].pid, p[i].at, p[i].bt, p[i].ct, p[i].tt, p[i].wt);
	}
	
	printf("\nGhant Chart\n");
	for(i=0;i<len;i++)
		printf("-------");
	printf("\n");
	for(i=0;i<len;i++){
		if (pid[i]!=-1)
			printf("  P%d  |",pid[i]);
		else
			printf(" IDLE |");
	}
	printf("\n");
	for(i=0;i<len;i++)
		printf("-------");
	printf("\n");
	printf("0     ");
	for(i=0;i<len;i++){
		printf("%d      ",ct[i]);	
	}
	printf("\n\n");
	
	printf("Average TurnAround Time: %.2f\n", (float)tottt/n);
	printf("Average Waiting Time: %.2f\n", (float)totwt/n);
}