I want to create a circular queue using a linked list. I also want to create many instances of that data structure (queue) without repeating the code.
This is what I came up with:
#include <stdio.h>
#include <stdlib.h>
struct queue
{
int info;
struct queue *next;
struct queue *front;
struct queue *rear;
};
void create(struct queue **q)
{
(*q)->next = 0;
(*q)->front = 0;
(*q)->rear = 0;
}
struct queue* makenode(int item){
struct queue* p = (struct queue*)malloc(sizeof (struct queue));
if (p) p->info = item;
return p;
}
void addLast(struct queue **q, int item){
struct queue* p = makenode(item);
if ((*q)->front == NULL){
(*q)->front = (*q)->rear = p;
(*q)->front->next = (*q)->front;
(*q)->rear->next = (*q)->rear;
}
else
{
(*q)->rear->next = p;
p->next = (*q)->front;
(*q)->rear = p;
}
}
int delFirst(struct queue **q){
struct queue *p = (*q)->front;
if ((*q)->front == 0)
printf("\nEmpty Queue\n");
else
{
int temp = (*q)->front->info;
if (((*q)->front->next) != ((*q)->front))
{
(*q)->front = (*q)->front->next;
(*q)->rear->next = (*q)->front;
}
else
{
(*q)->front = 0;
}
return temp;
}
free(p);
}
void main()
{
struct queue *premium, *normal;
create(&premium);
create(&normal);
addLast(&premium, 5);
addLast(&premium, 10);
addLast(&normal, 20);
addLast(&normal, 30);
printf("%i\n", delFirst(&premium));
printf("%i\n", delFirst(&premium));
delFirst(&premium);
printf("%i\n", delFirst(&normal));
printf("%i\n", delFirst(&normal));
delFirst(&normal);
getch();
}
Is there a better way to do this? I feel that my code is complicated. I am new to C programming and I only learned basics about queues and linked list. I don't know even my code is 100% right or an elegant code.
I compiled this code using DevC++ and it works fine, but when I compile it using MS Visual Studio 2013, it gave me an exception:
Access violation writing location....
I am very sure my code is not that good.