C Program to Implement Circular Linked List

#include<stdio.h>
#include<stdlib.h>
struct Node;
typedef struct Node * PtrToNode;
typedef PtrToNode List;
typedef PtrToNode Position;

struct Node
{
	int e;
	Position next;
};

void Insert(int x, List l, Position p)
{
	Position TmpCell;
	TmpCell = (struct Node*) malloc(sizeof(struct Node));
	if(TmpCell == NULL)
		printf("Memory out of space\n");
	else
	{
		TmpCell->e = x;
		TmpCell->next = p->next;
		p->next = TmpCell;
	}
}


int isLast(Position p, List l)
{
	return (p->next == l);
}

Position FindPrevious(int x, List l)
{
	Position p = l;
	while(p->next != l && p->next->e != x)
		p = p->next;
	return p;
}

Position Find(int x, List l)
{
	Position p = l->next;
	while(p != l && p->e != x)
		p = p->next;
	return p;
}

void Delete(int x, List l)
{
	Position p, TmpCell;
	p = FindPrevious(x, l);
	if(!isLast(p, l))
	{
		TmpCell = p->next;
		p->next = TmpCell->next;
		free(TmpCell);
	}
	else
		printf("Element does not exist!!!\n");
}

void Display(List l)
{
	printf("The list element are :: ");
	Position p = l->next;
	while(p != l)
	{
		printf("%d -> ", p->e);
		p = p->next;
	}
}

void main()
{
	int x, pos, ch, i;
	List l, l1;
	l = (struct Node *) malloc(sizeof(struct Node));
	l->next = l;
	List p = l;
	printf("CIRCULAR LINKED LIST IMPLEMENTATION OF LIST ADT\n\n");
	do
	{
		printf("\n\n1. INSERT\t 2. DELETE\t 3. FIND\t 4. PRINT\t 5. QUIT\n\nEnter the choice :: ");
		scanf("%d", &ch);
		switch(ch)
		{
			case 1:
				p = l;
				printf("Enter the element to be inserted :: ");
				scanf("%d",&x);
				printf("Enter the position of the element :: ");
				scanf("%d",&pos);
				for(i = 1; i < pos; i++)
				{
					p = p->next;
				}
				Insert(x,l,p);
				break;

			case 2:
				p = l;
				printf("Enter the element to be deleted :: ");
				scanf("%d",&x);
				Delete(x,p);
				break;

			case 3:
				p = l;
				printf("Enter the element to be searched :: ");
				scanf("%d",&x);
				p = Find(x,p);
				if(p == l)
					printf("Element does not exist!!!\n");
				else
					printf("Element exist!!!\n");
				break;

			case 4:
				Display(l);
				break;
		}
	}while(ch<5);
	return 0;
}

 OUTPUT:

CIRCULAR LINKED LIST IMPLEMENTATION OF LIST ADT



1. INSERT        2. DELETE       3. FIND         4. PRINT        5. QUIT

Enter the choice :: 1
Enter the element to be inserted :: 10
Enter the position of the element :: 1


1. INSERT        2. DELETE       3. FIND         4. PRINT        5. QUIT

Enter the choice :: 1
Enter the element to be inserted :: 20
Enter the position of the element :: 2


1. INSERT        2. DELETE       3. FIND         4. PRINT        5. QUIT

Enter the choice :: 1
Enter the element to be inserted :: 30
Enter the position of the element :: 3


1. INSERT        2. DELETE       3. FIND         4. PRINT        5. QUIT

Enter the choice :: 4
The list element are :: 10 -> 20 -> 30 ->

1. INSERT        2. DELETE       3. FIND         4. PRINT        5. QUIT

Enter the choice :: 5