# Remove all Fibonacci Nodes from a Circular Singly Linked List

Given a circular singly linked list containing N nodes, the task is to remove all the nodes from the list which contains Fibonacci data values.

Examples:

Input: CLL = 9 -> 11 -> 34 -> 6 -> 13 -> 20
Output: 9 -> 11 -> 6 -> 20
Explanation:
The list contains 2 fibonacci data values 32 and 13.
Therefore, the nodes containing this data has been deleted

Input: 5 -> 11 -> 16 -> 21 -> 17 -> 10
Output: 11 -> 16 -> 17 -> 10
Explanation:
The list contains 2 fibonacci data values 5 and 21.
Therefore, the nodes containing this data has been deleted

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The idea is to use hashing to precompute and store the Fibonacci numbers, and then check if a node contains a Fibonacci value in O(1) time.

1. Traverse through the entire circular singly linked list and obtain the maximum value in the list.
2. Now, in order to check for the Fibonacci numbers, build a hash table containing all the Fibonacci numbers less than or equal to the maximum value in the circular singly linked list.
3. Finally, traverse the nodes of the circular singly linked list one by one and check if the node contains Fibonacci numbers as their data value. Remove the nodes which have Fibonacci value.

Below is the implementation of the above idea:

## C++

 `// C++ program to delete all the ` `// Fibonacci nodes from the ` `// circular singly linked list ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Structure for a node ` `struct` `Node { ` `    ``int` `data; ` `    ``struct` `Node* next; ` `}; ` ` `  `// Function to insert a node at the beginning ` `// of a Circular linked list ` `void` `push(``struct` `Node** head_ref, ``int` `data) ` `{ ` `    ``// Create a new node and make head as next ` `    ``// of it. ` `    ``struct` `Node* ptr1 ` `        ``= (``struct` `Node*)``malloc``( ` `            ``sizeof``(``struct` `Node)); ` `    ``struct` `Node* temp = *head_ref; ` `    ``ptr1->data = data; ` `    ``ptr1->next = *head_ref; ` ` `  `    ``// If linked list is not NULL then ` `    ``// set the next of last node ` `    ``if` `(*head_ref != NULL) { ` ` `  `        ``// Find the node before head ` `        ``// and update next of it. ` `        ``while` `(temp->next != *head_ref) ` `            ``temp = temp->next; ` ` `  `        ``temp->next = ptr1; ` `    ``} ` `    ``else` ` `  `        ``// Point for the first node ` `        ``ptr1->next = ptr1; ` ` `  `    ``*head_ref = ptr1; ` `} ` ` `  `// Delete the node from a Circular Linked list ` `void` `deleteNode(Node* head_ref, Node* del) ` `{ ` `    ``struct` `Node* temp = head_ref; ` ` `  `    ``// If node to be deleted is head node ` `    ``if` `(head_ref == del) ` `        ``head_ref = del->next; ` ` `  `    ``// Traverse list till not found ` `    ``// delete node ` `    ``while` `(temp->next != del) { ` `        ``temp = temp->next; ` `    ``} ` ` `  `    ``// Copy the address of the node ` `    ``temp->next = del->next; ` ` `  `    ``// Finally, free the memory ` `    ``// occupied by del ` `    ``free``(del); ` ` `  `    ``return``; ` `} ` ` `  `// Function to find the maximum ` `// node of the circular linked list ` `int` `largestElement(``struct` `Node* head_ref) ` `{ ` `    ``// Pointer for traversing ` `    ``struct` `Node* current; ` ` `  `    ``// Initialize head to the current pointer ` `    ``current = head_ref; ` ` `  `    ``// Initialize min int value to max ` `    ``int` `maxEle = INT_MIN; ` ` `  `    ``// While the last node is not reached ` `    ``do` `{ ` ` `  `        ``// If current node data is ` `        ``// greater for max then replace it ` `        ``if` `(current->data > maxEle) { ` `            ``maxEle = current->data; ` `        ``} ` ` `  `        ``current = current->next; ` `    ``} ``while` `(current != head_ref); ` ` `  `    ``return` `maxEle; ` `} ` ` `  `// Function to create hash table to ` `// check Fibonacci numbers ` `void` `createHash(set<``int``>& hash, ` `                ``int` `maxElement) ` `{ ` `    ``int` `prev = 0, curr = 1; ` ` `  `    ``// Adding the first two elements ` `    ``// to the hash ` `    ``hash.insert(prev); ` `    ``hash.insert(curr); ` ` `  `    ``// Inserting the Fibonacci numbers ` `    ``// into the hash ` `    ``while` `(curr <= maxElement) { ` `        ``int` `temp = curr + prev; ` `        ``hash.insert(temp); ` `        ``prev = curr; ` `        ``curr = temp; ` `    ``} ` `} ` ` `  `// Function to delete all the Fibonacci nodes ` `// from the singly circular linked list ` `void` `deleteFibonacciNodes(Node* head) ` `{ ` `    ``// Find the largest node value ` `    ``// in Circular Linked List ` `    ``int` `maxEle = largestElement(head); ` ` `  `    ``// Creating a hash containing ` `    ``// all the Fibonacci numbers ` `    ``// upto the maximum data value ` `    ``// in the circular linked list ` `    ``set<``int``> hash; ` `    ``createHash(hash, maxEle); ` ` `  `    ``struct` `Node* ptr = head; ` ` `  `    ``struct` `Node* next; ` ` `  `    ``// Traverse the list till the end ` `    ``do` `{ ` ` `  `        ``// If the node's data is Fibonacci, ` `        ``// delete node 'ptr' ` `        ``if` `(hash.find(ptr->data) ` `            ``!= hash.end()) ` `            ``deleteNode(head, ptr); ` ` `  `        ``// Point to the next node ` `        ``next = ptr->next; ` `        ``ptr = next; ` ` `  `    ``} ``while` `(ptr != head); ` `} ` ` `  `// Function to print nodes in a ` `// given Circular linked list ` `void` `printList(``struct` `Node* head) ` `{ ` `    ``struct` `Node* temp = head; ` `    ``if` `(head != NULL) { ` `        ``do` `{ ` `            ``printf``(``"%d "``, temp->data); ` `            ``temp = temp->next; ` `        ``} ``while` `(temp != head); ` `    ``} ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``// Initialize lists as empty ` `    ``struct` `Node* head = NULL; ` ` `  `    ``// Created linked list will be ` `    ``// 9->11->34->6->13->20 ` `    ``push(&head, 20); ` `    ``push(&head, 13); ` `    ``push(&head, 6); ` `    ``push(&head, 34); ` `    ``push(&head, 11); ` `    ``push(&head, 9); ` ` `  `    ``deleteFibonacciNodes(head); ` ` `  `    ``printList(head); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to delete all the ` `// Fibonacci nodes from the ` `// circular singly linked list ` `import` `java.util.*; ` ` `  `class` `GFG{ ` `  `  `// Structure for a node ` `static` `class` `Node { ` `    ``int` `data; ` `    ``Node next; ` `}; ` `  `  `// Function to insert a node at the beginning ` `// of a Circular linked list ` `static` `Node push(Node head_ref, ``int` `data) ` `{ ` `    ``// Create a new node and make head as next ` `    ``// of it. ` `    ``Node ptr1 = ``new` `Node(); ` `    ``Node temp = head_ref; ` `    ``ptr1.data = data; ` `    ``ptr1.next = head_ref; ` `  `  `    ``// If linked list is not null then ` `    ``// set the next of last node ` `    ``if` `(head_ref != ``null``) { ` `  `  `        ``// Find the node before head ` `        ``// and update next of it. ` `        ``while` `(temp.next != head_ref) ` `            ``temp = temp.next; ` `  `  `        ``temp.next = ptr1; ` `    ``} ` `    ``else` `  `  `        ``// Point for the first node ` `        ``ptr1.next = ptr1; ` `  `  `    ``head_ref = ptr1; ` `    ``return` `head_ref; ` `} ` `  `  `// Delete the node from a Circular Linked list ` `static` `void` `deleteNode(Node head_ref, Node del) ` `{ ` `    ``Node temp = head_ref; ` `  `  `    ``// If node to be deleted is head node ` `    ``if` `(head_ref == del) ` `        ``head_ref = del.next; ` `  `  `    ``// Traverse list till not found ` `    ``// delete node ` `    ``while` `(temp.next != del) { ` `        ``temp = temp.next; ` `    ``} ` `  `  `    ``// Copy the address of the node ` `    ``temp.next = del.next; ` `  `  `    ``// Finally, free the memory ` `    ``// occupied by del ` `    ``del = ``null``; ` `  `  `    ``return``; ` `} ` `  `  `// Function to find the maximum ` `// node of the circular linked list ` `static` `int` `largestElement(Node head_ref) ` `{ ` `    ``// Pointer for traversing ` `    ``Node current; ` `  `  `    ``// Initialize head to the current pointer ` `    ``current = head_ref; ` `  `  `    ``// Initialize min int value to max ` `    ``int` `maxEle = Integer.MIN_VALUE; ` `  `  `    ``// While the last node is not reached ` `    ``do` `{ ` `  `  `        ``// If current node data is ` `        ``// greater for max then replace it ` `        ``if` `(current.data > maxEle) { ` `            ``maxEle = current.data; ` `        ``} ` `  `  `        ``current = current.next; ` `    ``} ``while` `(current != head_ref); ` `  `  `    ``return` `maxEle; ` `} ` `  `  `// Function to create hash table to ` `// check Fibonacci numbers ` `static` `void` `createHash(HashSet hash, ` `                ``int` `maxElement) ` `{ ` `    ``int` `prev = ``0``, curr = ``1``; ` `  `  `    ``// Adding the first two elements ` `    ``// to the hash ` `    ``hash.add(prev); ` `    ``hash.add(curr); ` `  `  `    ``// Inserting the Fibonacci numbers ` `    ``// into the hash ` `    ``while` `(curr <= maxElement) { ` `        ``int` `temp = curr + prev; ` `        ``hash.add(temp); ` `        ``prev = curr; ` `        ``curr = temp; ` `    ``} ` `} ` `  `  `// Function to delete all the Fibonacci nodes ` `// from the singly circular linked list ` `static` `void` `deleteFibonacciNodes(Node head) ` `{ ` `    ``// Find the largest node value ` `    ``// in Circular Linked List ` `    ``int` `maxEle = largestElement(head); ` `  `  `    ``// Creating a hash containing ` `    ``// all the Fibonacci numbers ` `    ``// upto the maximum data value ` `    ``// in the circular linked list ` `    ``HashSet hash = ``new` `HashSet(); ` `    ``createHash(hash, maxEle); ` `  `  `    ``Node ptr = head; ` `  `  `    ``Node next; ` `  `  `    ``// Traverse the list till the end ` `    ``do` `{ ` `  `  `        ``// If the node's data is Fibonacci, ` `        ``// delete node 'ptr' ` `        ``if` `(hash.contains(ptr.data)) ` `            ``deleteNode(head, ptr); ` `  `  `        ``// Point to the next node ` `        ``next = ptr.next; ` `        ``ptr = next; ` `  `  `    ``} ``while` `(ptr != head); ` `} ` `  `  `// Function to print nodes in a ` `// given Circular linked list ` `static` `void` `printList(Node head) ` `{ ` `    ``Node temp = head; ` `    ``if` `(head != ``null``) { ` `        ``do` `{ ` `            ``System.out.printf(``"%d "``, temp.data); ` `            ``temp = temp.next; ` `        ``} ``while` `(temp != head); ` `    ``} ` `} ` `  `  `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``// Initialize lists as empty ` `    ``Node head = ``null``; ` `  `  `    ``// Created linked list will be ` `    ``// 9.11.34.6.13.20 ` `    ``head = push(head, ``20``); ` `    ``head = push(head, ``13``); ` `    ``head = push(head, ``6``); ` `    ``head = push(head, ``34``); ` `    ``head = push(head, ``11``); ` `    ``head = push(head, ``9``); ` `  `  `    ``deleteFibonacciNodes(head); ` `  `  `    ``printList(head); ` `} ` `} ` ` `  `// This code is contributed by 29AjayKumar `

## C#

 `// C# program to delete all the ` `// Fibonacci nodes from the ` `// circular singly linked list ` `using` `System; ` `using` `System.Collections.Generic; ` ` `  `class` `GFG{ ` `   `  `// Structure for a node ` `class` `Node { ` `    ``public` `int` `data; ` `    ``public` `Node next; ` `}; ` `   `  `// Function to insert a node at the beginning ` `// of a Circular linked list ` `static` `Node push(Node head_ref, ``int` `data) ` `{ ` `    ``// Create a new node and make head as next ` `    ``// of it. ` `    ``Node ptr1 = ``new` `Node(); ` `    ``Node temp = head_ref; ` `    ``ptr1.data = data; ` `    ``ptr1.next = head_ref; ` `   `  `    ``// If linked list is not null then ` `    ``// set the next of last node ` `    ``if` `(head_ref != ``null``) { ` `   `  `        ``// Find the node before head ` `        ``// and update next of it. ` `        ``while` `(temp.next != head_ref) ` `            ``temp = temp.next; ` `   `  `        ``temp.next = ptr1; ` `    ``} ` `    ``else` `   `  `        ``// Point for the first node ` `        ``ptr1.next = ptr1; ` `   `  `    ``head_ref = ptr1; ` `    ``return` `head_ref; ` `} ` `   `  `// Delete the node from a Circular Linked list ` `static` `void` `deleteNode(Node head_ref, Node del) ` `{ ` `    ``Node temp = head_ref; ` `   `  `    ``// If node to be deleted is head node ` `    ``if` `(head_ref == del) ` `        ``head_ref = del.next; ` `   `  `    ``// Traverse list till not found ` `    ``// delete node ` `    ``while` `(temp.next != del) { ` `        ``temp = temp.next; ` `    ``} ` `   `  `    ``// Copy the address of the node ` `    ``temp.next = del.next; ` `   `  `    ``// Finally, free the memory ` `    ``// occupied by del ` `    ``del = ``null``; ` `   `  `    ``return``; ` `} ` `   `  `// Function to find the maximum ` `// node of the circular linked list ` `static` `int` `largestElement(Node head_ref) ` `{ ` `    ``// Pointer for traversing ` `    ``Node current; ` `   `  `    ``// Initialize head to the current pointer ` `    ``current = head_ref; ` `   `  `    ``// Initialize min int value to max ` `    ``int` `maxEle = ``int``.MinValue; ` `   `  `    ``// While the last node is not reached ` `    ``do` `{ ` `   `  `        ``// If current node data is ` `        ``// greater for max then replace it ` `        ``if` `(current.data > maxEle) { ` `            ``maxEle = current.data; ` `        ``} ` `   `  `        ``current = current.next; ` `    ``} ``while` `(current != head_ref); ` `   `  `    ``return` `maxEle; ` `} ` `   `  `// Function to create hash table to ` `// check Fibonacci numbers ` `static` `void` `createHash(HashSet<``int``> hash, ` `                ``int` `maxElement) ` `{ ` `    ``int` `prev = 0, curr = 1; ` `   `  `    ``// Adding the first two elements ` `    ``// to the hash ` `    ``hash.Add(prev); ` `    ``hash.Add(curr); ` `   `  `    ``// Inserting the Fibonacci numbers ` `    ``// into the hash ` `    ``while` `(curr <= maxElement) { ` `        ``int` `temp = curr + prev; ` `        ``hash.Add(temp); ` `        ``prev = curr; ` `        ``curr = temp; ` `    ``} ` `} ` `   `  `// Function to delete all the Fibonacci nodes ` `// from the singly circular linked list ` `static` `void` `deleteFibonacciNodes(Node head) ` `{ ` `    ``// Find the largest node value ` `    ``// in Circular Linked List ` `    ``int` `maxEle = largestElement(head); ` `   `  `    ``// Creating a hash containing ` `    ``// all the Fibonacci numbers ` `    ``// upto the maximum data value ` `    ``// in the circular linked list ` `    ``HashSet<``int``> hash = ``new` `HashSet<``int``>(); ` `    ``createHash(hash, maxEle); ` `   `  `    ``Node ptr = head; ` `   `  `    ``Node next; ` `   `  `    ``// Traverse the list till the end ` `    ``do` `{ ` `   `  `        ``// If the node's data is Fibonacci, ` `        ``// delete node 'ptr' ` `        ``if` `(hash.Contains(ptr.data)) ` `            ``deleteNode(head, ptr); ` `   `  `        ``// Point to the next node ` `        ``next = ptr.next; ` `        ``ptr = next; ` `   `  `    ``} ``while` `(ptr != head); ` `} ` `   `  `// Function to print nodes in a ` `// given Circular linked list ` `static` `void` `printList(Node head) ` `{ ` `    ``Node temp = head; ` `    ``if` `(head != ``null``) { ` `        ``do` `{ ` `            ``Console.Write(``"{0} "``, temp.data); ` `            ``temp = temp.next; ` `        ``} ``while` `(temp != head); ` `    ``} ` `} ` `   `  `// Driver code ` `public` `static` `void` `Main(String[] args) ` `{ ` `    ``// Initialize lists as empty ` `    ``Node head = ``null``; ` `   `  `    ``// Created linked list will be ` `    ``// 9.11.34.6.13.20 ` `    ``head = push(head, 20); ` `    ``head = push(head, 13); ` `    ``head = push(head, 6); ` `    ``head = push(head, 34); ` `    ``head = push(head, 11); ` `    ``head = push(head, 9); ` `   `  `    ``deleteFibonacciNodes(head); ` `   `  `    ``printList(head); ` `} ` `} ` ` `  `// This code is contributed by PrinciRaj1992 `

Output:

```9 11 6 20
```

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Improved By : 29AjayKumar, princiraj1992