Circularlinkedlist_dsa.c

#include <stdio.h>
#include <conio.h>
#include <malloc.h>
struct node
{
    int data;
    struct node *next;
};
struct node *start = NULL;
struct node *create_ll(struct node *);
struct node *display(struct node *);
struct node *insert_beg(struct node *);
struct node *insert_end(struct node *);
struct node *delete_beg(struct node *);
struct node *delete_end(struct node *);
struct node *delete_after(struct node *);
struct node *delete_list(struct node *);

int main()
{
int option;
//clrscr();
do
{
printf("\n\n ***** MAIN MENU *****");
printf("\n 1: Create a list");
printf("\n 2: Display the list");
printf("\n 3: Add a node at the beginning");
printf("\n 4: Add a node at the end");
printf("\n 5: Delete a node from the beginning");
printf("\n 6: Delete a node from the end");
printf("\n 7: Delete a node after a given node");
printf("\n 8: Delete the entire list");
printf("\n 9: Exit");
printf("\n\n Enter your option : ");
scanf("%d", &option);
switch(option)
{
case 1: start = create_ll(start);
printf("\n CIRCULAR LINKED LIST CREATED");
break;
case 2: start = display(start);
break;
case 3: start = insert_beg(start);
break;
case 4: start = insert_end(start);
break;
case 5: start = delete_beg(start);
break;
case 6: start = delete_end(start);
break;
case 7: start = delete_after(start);
break;
case 8: start = delete_list(start);
printf("\n CIRCULAR LINKED LIST DELETED");
break;
}
} while(option != 9);
getch();
return 0;
}
struct node *create_ll(struct node *start)
{
struct node *new_node, *ptr;
int num;
printf("\n Enter -1 to end");
printf("\n Enter the data : ");
scanf("%d", &num);
while(num != -1)
{
new_node = (struct node*)malloc(sizeof(struct node));
new_node -> data = num;
if(start == NULL)
{
new_node -> next = new_node;
start = new_node;
}
else
{
ptr = start;
while(ptr->next!=start)
ptr = ptr->next;
ptr->next = new_node;
new_node ->next = start;
}
printf("\n Enter the data : ");
scanf("%d", &num);
}
return start;
}



struct node *display(struct node *start)
{
struct node *ptr;
ptr = start;
while(ptr->next != start)
{
printf("\t %d", ptr -> data);
ptr = ptr -> next;
}
printf("\t %d", ptr -> data);
return start;
}



struct node *insert_beg(struct node *start)
{
struct node *new_node, *ptr;
int num;
printf("\n Enter the data : ");
scanf("%d", &num);
new_node = (struct node*)malloc(sizeof(struct node));
new_node -> data = num;
ptr = start;
while(ptr->next != start)
ptr = ptr -> next;
ptr->next = new_node;
new_node -> next = start;
start = new_node;
return start;
}



struct node *insert_end(struct node *start)
{
struct node *ptr, *new_node;
int num;
printf("\n Enter the data : ");
scanf("%d", &num);
new_node = (struct node*)malloc(sizeof(struct node));
new_node -> data = num;
ptr = start;
while(ptr -> next != start)
ptr = ptr -> next;
ptr -> next = new_node;
new_node -> next = start;
return start;
}



struct node *delete_beg(struct node *start)
{
struct node *ptr;
ptr = start;
while(ptr -> next != start)
ptr = ptr -> next;
ptr -> next = start -> next;
free(start);
start = ptr -> next;
return start;
}



struct node *delete_end(struct node *start)
{
struct node *ptr, *preptr;
ptr = start;
while(ptr -> next != start)
{
preptr = ptr;
ptr = ptr -> next;
}
preptr -> next = ptr -> next;
free(ptr);
return start;
}



struct node *delete_after(struct node *start)
{
struct node *ptr, *preptr;
int val;
printf("\n Enter the value after which the node has to be deleted : ");
scanf("%d", &val);
ptr = start;
preptr = ptr;
while(preptr -> data != val)
{
preptr = ptr;
ptr = ptr -> next;
}
preptr -> next = ptr -> next;
if(ptr == start)
start = preptr -> next;
free(ptr);
return start;
}



struct node *delete_list(struct node *start)
{
struct node *ptr;
ptr = start;
while(ptr -> next != start)
start = delete_end(start);
free(start);
return start;
}