Circular Single Linked List

# include <stdio.h>
# include <conio.h>
# include <stdlib.h>
struct cslinklist
{
int data;
struct cslinklist *next;
};
typedef struct cslinklist node;
node *start = NULL;
int nodectr;
node* getnode()
{
node * newnode;
newnode = (node *) malloc(sizeof(node));
printf("\n Enter data: ");
scanf("%d", &newnode -> data);
newnode -> next = NULL;
return newnode;
}
int menu()
{
int ch;
clrscr();
printf("\n 1. Create a list ");
printf("\n\n--------------------------");
printf("\n 2. Insert a node at beginning ");
printf("\n 3. Insert a node at end");
printf("\n 4. Insert a node at middle");
printf("\n\n--------------------------");
printf("\n 5. Delete a node from beginning");
printf("\n 6. Delete a node from Last");
printf("\n 7. Delete a node from Middle");
printf("\n\n--------------------------");
printf("\n 8. Display the list");
printf("\n 9. Exit");
printf("\n\n--------------------------");
printf("\n Enter your choice: ");
scanf("%d", &ch);
return ch;
}
void createlist(int n)
{
int i;
node *newnode;
node *temp;
nodectr = n;
for(i = 0; i < n ; i++)
{
newnode = getnode();
if(start == NULL)
{
start = newnode;
}
else
{
temp = start;
while(temp -> next != NULL)
temp = temp -> next;
temp -> next = newnode;
}
}
newnode ->next = start; /* last node is pointing to starting node */
}
void display()
{
node *temp;
temp = start;
printf("\n The contents of List (Left to Right): ");
if(start == NULL )
printf("\n Empty List");
else
{
do
{
printf("\t %d ", temp -> data);
temp = temp -> next;
} while(temp != 
start); printf(" X ");
}
}
void cll_insert_beg()
{
node *newnode, *last;
newnode = getnode();
if(start == NULL)
{
start = newnode;
newnode -> next = start;
}
else
{
last = start;
while(last -> next != start)
last = last -> next;
newnode -> next = start;
start = newnode;
last -> next = start;
}
printf("\n Node inserted at beginning..");
nodectr++;
}
void cll_insert_end()
{
node *newnode, *temp;
newnode = getnode();
if(start == NULL )
{
start = newnode;
newnode -> next = start;
}
else
{
temp = start;
while(temp -> next != start)
temp = temp -> next;
temp -> next = newnode;
newnode -> next = start;
}
printf("\n Node inserted at end..");
nodectr++;
}
void cll_insert_mid()
{
node *newnode, *temp, *prev;
int i, pos ;
newnode = getnode();
printf("\n Enter the position: ");
scanf("%d", &pos);
if(pos > 1 && pos < nodectr)
{
temp = start;
prev = temp;
i = 1;
while(i < pos)
{
prev = temp;
temp = temp -> next;
i++;
}
prev -> next = newnode;
newnode -> next = temp;
nodectr++;
printf("\n Node inserted at middle..");
}
else
{
printf("position %d of list is not a middle position ", pos);
}
}
void cll_delete_beg()
{
node *temp, *last;
if(start == NULL)
{
printf("\n No nodes exist..");
getch();
return ;
}
else
{
last = temp = start;
while(last -> next != start)
last = last -> next;
start = start -> next;
last -> next = start;
free(temp);
nodectr--;
printf("\n Node deleted..");
if(nodectr == 0)
start = NULL;
}
}
void cll_delete_last()
{
node *temp,*prev;
if(start == NULL)
{
printf("\n No nodes exist..");
getch();
return ;
}
else
{
temp = start;
prev = start;
while(temp -> next != start)
{
prev = temp;
temp = temp -> next;
}
prev -> next = start;
free(temp);
nodectr--;
if(nodectr == 0)
start = NULL;
printf("\n Node deleted..");
}
}
void cll_delete_mid()
{
int i = 0, pos;
node *temp, *prev;
if(start == NULL)
{
printf("\n No nodes exist..");
getch();
return ;
}
else
{
printf("\n Which node to delete: ");
scanf("%d", &pos);
if(pos > nodectr)
{
printf("\nThis node does not exist");
getch();
return;
}
if(pos > 1 && pos < nodectr)
{
temp=start;
prev = start;
i = 0;
while(i < pos - 1)
{
prev = temp;
temp = temp -> next ;
i++;
}
prev -> next = temp -> next;
free(temp);
nodectr--;
printf("\n Node Deleted..");
}
else
{
printf("\n It is not a middle position..");
getch();
}
}
}
void main(void)
{
int result;
int ch, n;
clrscr();
while(1)
{
ch = menu();
switch(ch)
{
case 1 :
if(start == NULL)
{
printf("\n Enter Number of nodes to create: ");
scanf("%d", &n);
createlist(n);
printf("\nList created..");
}
else
printf("\n List is already Exist..");
break;
case 2 :
cll_insert_beg();
break;
case 3 :
cll_insert_end();
break;
case 4 :
cll_insert_mid();
break;
case 5 :
cll_delete_beg();
break;
case 6 :
cll_delete_last();
break;
case 7 :
cll_delete_mid();
break;
case 8 :
display();
break;
case 9 :
exit(0);
}
getch();
}
}