C Programming Code Examples
C > Beginners Lab Assignments Code Examples
Implement various Queue Functions using Dynamic Memory Allocation
/* Implement various Queue Functions using Dynamic Memory Allocation
- Use malloc function to allocate memory.
- Define separate functions for the operations like insert, delete and display.
- Use switch statement to access these functions. */
#include <stdio.h>
#include <stdlib.h>
#define MAX 10
struct node
{
int data;
struct node *link;
}*front, *rear;
// function protypes
void insert();
void delete();
void queue_size();
void check();
void first_element();
void main()
{
int choice, value;
while(1)
{
printf("enter the choice \n");
printf("1 : create an empty queue \n2 : Insert element\n");
printf("3 : Dequeue an element \n4 : Check if empty\n");
printf("5. Get the first element of the queue\n");
printf("6. Get the number of entries in the queue\n");
printf("7. Exit\n");
scanf("%d", &choice);
switch (choice) // menu driven program
{
case 1:
printf("Empty queue is created with a capacity of %d\n", MAX);
break;
case 2:
insert();
break;
case 3:
delete();
break;
case 4:
check();
break;
case 5:
first_element();
break;
case 6:
queue_size();
break;
case 7:
exit(0);
default:
printf("wrong choice\n");
break;
}
}
}
// to insert elements in queue
void insert()
{
struct node *temp;
temp = (struct node*)malloc(sizeof(struct node));
printf("Enter value to be inserted \n");
scanf("%d", &temp->data);
temp->link = NULL;
if (rear == NULL)
{
front = rear = temp;
}
else
{
rear->link = temp;
rear = temp;
}
}
// delete elements from queue
void delete()
{
struct node *temp;
temp = front;
if (front == NULL)
{
printf("queue is empty \n");
front = rear = NULL;
}
else
{
printf("deleted element is %d\n", front->data);
front = front->link;
free(temp);
}
}
// check if queue is empty or not
void check()
{
if (front == NULL)
printf("\nQueue is empty\n");
else
printf("Elements are present in the queue \n");
}
// returns first element of queue
void first_element()
{
if (front == NULL)
{
printf(" The queue is empty \n");
}
else
printf(" The front element is %d \n", front->data);
}
// returns number of entries and displays the elements in queue
void queue_size()
{
struct node *temp;
temp = front;
int cnt = 0;
if (front == NULL)
{
printf(" queue empty \n");
}
while (temp)
{
printf("%d ", temp->data);
temp = temp->link;
cnt++;
}
printf(" size of queue is %d \n", cnt);
}
/*
- Ask the user for the operations like insert, delete, display etc.
- According to the entered option access the respective functions. Use switch statement to access the functions.
- Use structure with a data and a pointer as the data module. Use malloc function to assign the memory dynamically.
- In the insert() function ask the user to enter the number to be inserted and store the value into the new data module's data.
- In the delete() function delete the element at the front.
- In the check() function, check if the queue is empty or not.
- In the first_element() function, print the first element of the queue.
*/
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