Home > C Examples > Programs that implement Queue (its operations) using Pointers in C.

Programs that implement Queue (its operations) using Pointers in C.

#define true 1
#define false 0

#include<stdio.h>
#include<conio.h>
#include<process.h>

struct q_point
{
int ele;
struct q_point* n;
};

struct q_point *f_ptr = NULL;

int e_que(void);
void add_ele(int);
int rem_ele(void);
void show_ele();

/*main function*/
void main()
{
int ele,choice,j;
while(1)
{
clrscr();
printf("\n\n****IMPLEMENTATION OF QUEUE USING POINTERS****\n");
printf("==============================================");
printf("\n\t\t  MENU\n");
printf("==============================================");
printf("\n\t[1] To insert an element");
printf("\n\t[2] To remove an element");
printf("\n\t[3] To display all the elements");
printf("\n\t[4] Exit");
printf("\n\n\tEnter your choice:");
scanf("%d", &choice);

switch(choice)
{
case 1:
{
printf("\n\tElement to be inserted:");
scanf("%d",&ele);
add_ele(ele);
getch();
break;
}

case 2:
{
if(!e_que())
{
j=rem_ele();
printf("\n\t%d is removed from the queue",j);
getch();
}
else
{
printf("\n\tQueue is Empty.");
getch();
}
break;
}

case 3:
show_ele();
getch();
break;

case 4:
exit(1);
break;

default:
printf("\n\tInvalid choice.");
getch();
break;
}

}
}

/* Function to check if the queue is empty*/
int e_que(void)
{
if(f_ptr==NULL)
return true;
return false;
}

/* Function to add an element to the queue*/
void add_ele(int ele)
{
struct q_point *queue = (struct q_point*)malloc(sizeof(struct q_point));
queue->ele = ele;
queue->n = NULL;
if(f_ptr==NULL)
f_ptr = queue;
else
{
struct q_point* ptr;
ptr = f_ptr;
for(ptr=f_ptr ;ptr->n!=NULL; ptr=ptr->n);
ptr->n = queue;
}
}

/* Function to remove an element from the queue*/
int rem_ele()
{
struct q_point* queue=NULL;
if(e_que()==false)
{
int j = f_ptr->ele;
queue=f_ptr;
f_ptr = f_ptr->n;
free (queue);
return j;
}
else
{
printf("\n\tQueue is empty.");
return -9999;
}
}

/* Function to display the queue*/
void show_ele()
{
struct q_point *ptr=NULL;
ptr=f_ptr;
if(e_que())
{
printf("\n\tQUEUE is Empty.");
return;
}
else
{
printf("\n\tElements present in Queue are:\n\t");
while(ptr!=NULL)
{
printf("%d\t",ptr->ele);
ptr=ptr->n;
}
}
}
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Bug: An elusive creature living in a program that makes it incorrect. The activity of "debugging", or removing bugs from a program, ends when people get tired of doing it, not when the bugs are removed.

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