Circular_linked_list

//			Write a C Program to implement CIRCULAR LINKED LIST(one way).This Program must include following functions in it.
//			a.Write a function to CONSTRUCT a circular linked list.
//			b.Write a function to INSERT an element at the beginning of the created linked list(step a).
//			c.Write a function to INSERT an element at the end of the circular linked list.
//			d.Write a function to DELETE an element from the beginning of the circular linked list.
//			e.Write a function to DELETE an element from the end of the circular linkrd list.
//			f.Write a function for 'DISPLAY' operation which prints the content of the circular linked list.




#include<stdio.h>
#include<stdlib.h>
struct cr
	{
	int data;
	struct cr *next;
	}
	s1,*node,*start,*end,*temp;

int count=0;
void construct()
	{
	start=NULL;node=NULL;
	}
void insertb()
{
int x;
printf("Enter the element:"); scanf("%d",&x);
count++;
node=(struct cr *)malloc(sizeof(s1));
node->data=x;
if(start==NULL)
	{
	start=node;
	start->next=start;
	end=node;
	}
else
	{
	node->next=start;
	end->next=node;
	start=node;
	}
}
void inserte(){
int x;
printf("Enter the element:"); scanf("%d",&x);
count++;
node=(struct cr *)malloc(sizeof(s1));
node->data=x;
if(start==NULL)
	{
	start=node;
	start->next=start;
	end=node;
	}
else	
	{
	node->next=start;
	end->next=node;
	end=node;
	}
}
void deletee()
{
if(start==NULL)
	printf("Queue Underflow\n");
else if(start==end)
	{
	temp=end;
	free(temp);
	start=NULL;
	end=NULL;
	}
else
	{
	temp=end;
	count--;
for(node=start;node->next->next!=start;node=node->next);
	end=node;
	end->next=start;
	free(temp);
	}
}
void deleteb()
{
if(start==NULL)
	printf("Queue Underflow\n");
else if(start==end)
	{
	temp=end; 
	free(temp);
	start=NULL;
	end=NULL;
	}
else
	{
	temp=start;
	count--;
	start=start->next;
	end->next=start;
	free(temp);
	}
}
void display()
{
int i;
if(start==NULL) 
	printf("Queue underflow!\n");
else
	{
	printf("\nThe elements are:\n");
		for(node=start,i=0;i<count;i++,node=node->next)
		printf("%d ",node->data);
	}
}
void main()
{
int ch;
construct();
while(1)
{
printf("\n\n***Circular Queue***\n1.Insert at beginning\n2.Insert at end\n3.Delete from begining\n4.Delete from end\n5.Display\n6.Exit\nEnter your choice:\n");
scanf("%d",&ch);
switch(ch)
	{
	case 1: insertb(); break;
	case 2: inserte(); break;
	case 3: deleteb(); break;
	case 4: deletee(); break;
	case 5: display(); break;
	case 6: exit(0);   break;
	default: printf("\nWrong Choice!!\n");
	}
}
}