C Program to implement Singly Linked List to insert and delete a node at a specified position and display the contents of the Singly List

Program

#include<stdio.h>
#include<stdlib.h>
struct node
{
	int info;
	struct node *link;
};
typedef struct node *NODE;
NODE getnode()
{
	NODE x;
	x = (NODE) malloc(sizeof(struct node));
	if(x == NULL)
	{
		printf("Node creation error\n");
		return;
	}
	return x;
}
NODE insert_position(NODE first, int item, int pos)
{
	int count = 1;
	NODE temp, cur, prev;
	temp = getnode();
	temp->info = item;
	temp->link = NULL;
	if(first == NULL && pos == 1)
		return temp;
	if(first == NULL && pos > 1)
	{
		printf("Invalid position\n");
		free(temp);
		return first;
	}
	if(pos == 1)
	{
		temp->link = first;
		return temp;
	}
	cur = first;
	prev = NULL;
	while(cur != NULL && pos != count)
	{
		prev = cur;
		cur = cur->link;
		count++;
	}
	if(cur == NULL && pos > count)
	{
		printf("Invalid position\n");
		free(temp);
		return first;
	}
	prev->link = temp;
	temp->link = cur;
	return first;
}
NODE delete_position(NODE first, int pos)
{
	int count = 1;
	NODE temp, cur, prev;
	if(first == NULL)
	{
		printf("List is empty. Cannot delete\n");
		return first;
	}
	if(first->link == NULL && pos > 1)
	{
		printf("Invalid position to delete\n");
		return first;
	}
	if(pos == 1)
	{
		temp = first->link;
		free(first);
		return temp;
	}
	cur = first;
	prev = NULL;
	while(cur != NULL && pos != count)
	{
		prev = cur;
		cur = cur->link;
		count++;
	}
	if(cur == NULL && pos >= count)
	{
		printf("Invalid position to delete\n");
		return first;
	}
	prev->link = cur->link;
	printf("Item deleted is: %d\n", cur->info);
	free(cur);
	return first;
}
void display(NODE first)
{
	NODE cur;
	if(first == NULL)
	{
		printf("List is empty\n");
		return;
	}
	cur = first;
	while(cur != NULL)
	{
		printf("%d\n", cur->info);
		cur = cur->link;
	}
}
void main()
{
	int item, pos, choice;
	NODE first;
	for(;;)
	{
		printf("Enter the choice\n");
		printf("1. Insert position\n2. Delete position\n");
		printf("3. Display\n4. Exit\n");
		scanf("%d", &choice);
		switch(choice)
		{
			case 1:	printf("Enter the item to be inserted\n");
				scanf("%d", &item);
				printf("Enter the position\n");
				scanf("%d", &pos);
				first = insert_position(first, item, pos);
				break;
			case 2: printf("Enter the position to be deleted\n");
				scanf("%d", &pos);
				first = delete_position(first, pos);
				break;
			case 3: display(first);
				break;
			default:	exit(0);
		}
	}
}

Output

Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
2
Enter the position to be deleted
1
List is empty. Cannot delete
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
2
Enter the position to be deleted
2
List is empty. Cannot delete
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
1
Enter the item to be inserted
10
Enter the position
1
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
1
Enter the item to be inserted
20
Enter the position
2
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
1
Enter the item to be inserted
30
Enter the position
3
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
1
Enter the item to be inserted
40
Enter the position
4
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
1
Enter the item to be inserted
50
Enter the position
5
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
3 
10
20
30
40
50
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
2
Enter the position to be deleted
6
Invalid position to delete
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
2
Enter the position to be deleted
2
Item deleted is: 20
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
3
10
30
40
50
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
2
Enter the position to be deleted
1
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
3
30
40
50
Enter the choice
1. Insert position
2. Delete position
3. Display
4. Exit
4