C Program to implement Linear Queue using Singly Linked List

By: Koushik

Created: 02/28/2024 03:32

Last modified: 02/28/2024 03:32

Program

#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
struct node
{
	int info;
	struct node *link;
};
typedef struct node* NODE;
NODE getnode();
NODE enqueue(NODE , int);
NODE dequeue(NODE);
void display(NODE);
void main()
{
	NODE front;
	int choice, item;
	front = NULL;
	while(1)
	{
		printf("Enter\n");
		printf("1. Enqueue\n");
		printf("2. Dequeue\n");
		printf("3. Display\n");
		printf("4. Exit\n");
		scanf("%d", &choice);
		switch(choice)
		{
			case 1:
				printf("Enter item to be inserted\n");
				scanf("%d", &item);
				front = enqueue(front, item);
				break;
			case 2:
				front = dequeue(front);
				break;
			case 3:
				display(front);
				break;
			default:
				exit(0);
		}
	}
}
NODE getnode()
{
	NODE x;
	x = (NODE) malloc(sizeof(struct node));
	if(x == NULL)
	{
		printf("Node creation error\n");
		return;
	}
	return x;
}
NODE enqueue(NODE front , int item)
{
	NODE temp, current;
	temp = getnode();
	temp->info = item;
	temp->link = NULL;
	if(front == NULL)
	{
		return temp;
	}
	current = front;
	while(current->link != NULL)
	{
		current = current->link;
	}
	current->link = temp;
	return front;
}
NODE dequeue(NODE front)
{
	NODE temp;
	if(front == NULL)
	{
		printf("Cannot delete. Empty List\n");
		return front;
	}
	temp = front;
	front = front->link;
	printf("Deleted node is %d\n", temp->info);
	free(temp);
	return front;
}
void display(NODE front)
{
	NODE temp;
	if(front == NULL)
	{
		printf("Cannot print. Empty list\n");
		return;
	}
	temp = front;
	printf("Contents of queue is:\n");
	while(temp != NULL)
	{
		printf("%d\n", temp->info);
		temp = temp->link;
	}
	printf("\n");
}

Output

Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
3
Cannot print. Empty list
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
1
Enter item to be inserted
21
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
1
Enter item to be inserted
31
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
1
Enter item to be inserted
41
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
3
Contents of queue is:
21
31
41
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
2
Deleted node is 21
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
1
Enter item to be inserted
51
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
2
Deleted node is 31
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
1
Enter item to be inserted
11
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
1
Enter item to be inserted
30
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
3
Contents of queue is:
41
51
11
30
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
2
Deleted node is 41
Enter
1. Enqueue
2. Dequeue
3. Display
4. Exit
4