Delete all Non-Prime Nodes from a Singly Linked List

Given a singly linked list containing N nodes, the task is to delete all nodes from the list which are not prime.

Examples:

Input : List = 15 -> 16 -> 6 -> 7 -> 17
Output : Final List = 7 -> 17

Input : List = 15 -> 3 -> 4 -> 2 -> 9
Output : Final List = 3 ->2

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

Approach: The idea is to traverse the nodes of the singly linked list one by one and get the pointer of the nodes which are not prime. Delete those nodes by following the approach used in the post: Delete a node from Linked List.

Below is the implementation of above idea:

C++

// C++ implementation to delete all 
// non-prime nodes from the singly 
// linked list 
#include <bits/stdc++.h> 
  
using namespace std; 
  
// Node of the singly linked list 
struct Node { 
    int data; 
    Node* next; 
}; 
  
// function to insert a node at the beginning 
// of the singly Linked List 
void push(Node** head_ref, int new_data) 
{ 
    Node* new_node = new Node; 
    new_node->data = new_data; 
    new_node->next = (*head_ref); 
    (*head_ref) = new_node; 
} 
  
// Function to check if a number is prime 
bool isPrime(int n) 
{ 
    // Corner cases 
    if (n <= 1) 
        return false; 
    if (n <= 3) 
        return true; 
  
    // This is checked so that we can skip 
    // middle five numbers in below loop 
    if (n % 2 == 0 || n % 3 == 0) 
        return false; 
  
    for (int i = 5; i * i <= n; i = i + 6) 
        if (n % i == 0 || n % (i + 2) == 0) 
            return false; 
  
    return true; 
} 
  
// function to delete all non-prime nodes 
// from the singly linked list 
void deleteNonPrimeNodes(Node** head_ref) 
{ 
    // Remove all composite nodes at the beginning 
    Node* ptr = *head_ref; 
    while (ptr != NULL && !isPrime(ptr->data)) 
    { 
       Node *temp = ptr; 
       ptr = ptr->next; 
       delete(temp); 
    } 
    *head_ref = ptr; 
    if (ptr == NULL) 
       return; 
  
    // Remove remaining nodes 
    Node *curr = ptr->next; 
    while (curr != NULL) { 
  
        if (!isPrime(curr->data)) 
        { 
            ptr->next = curr->next; 
            delete(curr); 
            curr = ptr->next; 
        } 
        else
        { 
            ptr = curr; 
            curr = curr->next; 
        } 
     }     
} 
  
// function to print nodes in a 
// given singly linked list 
void printList(Node* head) 
{ 
    while (head != NULL) { 
        cout << head->data << " "; 
        head = head->next; 
    } 
} 
  
// Driver program 
int main() 
{ 
    // start with the empty list 
    Node* head = NULL; 
  
    // create the linked list 
    // 15 -> 16 -> 7 -> 6 -> 17 
    push(&head, 17); 
    push(&head, 7); 
    push(&head, 6); 
    push(&head, 16); 
    push(&head, 15); 
  
    cout << "Original List: "; 
    printList(head); 
  
    deleteNonPrimeNodes(&head); 
  
    cout << "\nModified List: "; 
    printList(head); 
} 

Java

// Java implementation to delete all  
// non-prime nodes from the singly  
// linked list 
class GFG 
{ 
      
// Node of the singly linked list  
static class Node 
{  
    int data;  
    Node next;  
};  
  
// function to insert a node at the beginning  
// of the singly Linked List  
static Node push(Node head_ref, int new_data)  
{  
    Node new_node = new Node();  
    new_node.data = new_data;  
    new_node.next = (head_ref);  
    (head_ref) = new_node;  
    return head_ref; 
}  
  
// Function to check if a number is prime  
static boolean isPrime(int n)  
{  
    // Corner cases  
    if (n <= 1)  
        return false;  
    if (n <= 3)  
        return true;  
  
    // This is checked so that we can skip  
    // middle five numbers in below loop  
    if (n % 2 == 0 || n % 3 == 0)  
        return false;  
  
    for (int i = 5; i * i <= n; i = i + 6)  
        if (n % i == 0 || n % (i + 2) == 0)  
            return false;  
  
    return true;  
}  
  
// function to delete all non-prime nodes  
// from the singly linked list  
static Node deleteNonPrimeNodes(Node head_ref)  
{  
    // Remove all composite nodes at the beginning  
    Node ptr = head_ref;  
    while (ptr != null && !isPrime(ptr.data))  
    {  
        Node temp = ptr;  
        ptr = ptr.next;  
    }  
    head_ref = ptr;  
    if (ptr == null)  
        return null;  
  
    // Remove remaining nodes  
    Node curr = ptr.next;  
    while (curr != null)  
    {  
  
        if (!isPrime(curr.data))  
        {  
            ptr.next = curr.next;  
            curr = ptr.next;  
        }  
        else
        {  
            ptr = curr;  
            curr = curr.next;  
        }  
    }  
    return head_ref; 
}  
  
// function to print nodes in a  
// given singly linked list  
static void printList(Node head)  
{  
    while (head != null) 
    {  
        System.out.print(head.data + " ");  
        head = head.next;  
    }  
}  
  
// Driver code  
public static void main(String args[])  
{  
    // start with the empty list  
    Node head = null;  
  
    // create the linked list  
    // 15 . 16 . 7 . 6 . 17  
    head = push(head, 17);  
    head = push(head, 7);  
    head = push(head, 6);  
    head = push(head, 16);  
    head = push(head, 15);  
  
    System.out.print("Original List: ");  
    printList(head);  
  
    head = deleteNonPrimeNodes(head);  
  
    System.out.print("\nModified List: ");  
    printList(head);  
}  
} 
  
// This code is contributed by Arnab Kundu 

Python3

# Python3 implementation to delete all 
# non-prime nodes from the singly 
# linked list 
import math  
  
# Node of the singly linked list 
class Node:  
    def __init__(self, data):  
        self.data = data  
        self.next = None
  
# function to insert a node at the beginning 
# of the singly Linked List 
def push(head_ref, new_data): 
    new_node = Node(new_data) 
    new_node.data = new_data 
    new_node.next = head_ref 
    head_ref = new_node 
    return head_ref 
  
# Function to check if a number is prime 
def isPrime(n): 
      
    # Corner cases 
    if (n <= 1): 
        return False
    if (n <= 3): 
        return True
  
    # This is checked so that we can skip 
    # middle five numbers in below loop 
    if (n % 2 == 0 or n % 3 == 0): 
        return False
    for i in range(5, n + 1, 6): 
        if (i * i < n + 2 and 
           (n % i == 0 or n % (i + 2) == 0)): 
            return False
          
    return True
  
# function to delete all non-prime nodes 
# from the singly linked list 
def deleteNonPrimeNodes(head_ref): 
      
    # Remove all composite nodes at the beginning 
    ptr = head_ref 
    while (ptr != None and 
           isPrime(ptr.data)!= True): 
        temp = ptr 
        ptr = ptr.next
        # delete(temp) 
      
    head_ref = ptr 
    if (ptr == None): 
        return None
  
    # Remove remaining nodes 
    curr = ptr.next
    while (curr != None) : 
  
        if (isPrime(curr.data) != True): 
            ptr.next = curr.next
            #delete(curr) 
            curr = ptr.next
          
        else: 
            ptr = curr 
            curr = curr.next
          
        return head_ref      
  
# function to print nodes in a 
# given singly linked list 
def printList( head): 
    while (head != None) : 
        print(head.data, end = " ") 
        head = head.next
      
# Driver Code 
if __name__=='__main__':  
  
    # start with the empty list 
    head = None
  
    # create the linked list 
    # 15 -> 16 -> 7 -> 6 -> 17 
    head = push(head, 17) 
    head = push(head, 7) 
    head = push(head, 6) 
    head = push(head, 16) 
    head = push(head, 15) 
  
    print("Original List: ") 
    printList(head) 
  
    head = deleteNonPrimeNodes(head) 
  
    print("\nModified List: ") 
    printList(head) 
  
# This code is contributed by AbhiThakur 

C#

// C# implementation to delete all  
// non-prime nodes from the singly  
// linked list  
using System; 
  
class GFG  
{ 
  
    // Node of the singly linked list  
    public class Node  
    { 
        public int data; 
        public Node next; 
    }; 
  
    // function to insert a node at the beginning  
    // of the singly Linked List  
    static Node push(Node head_ref, int new_data)  
    { 
        Node new_node = new Node(); 
        new_node.data = new_data; 
        new_node.next = (head_ref); 
        (head_ref) = new_node; 
        return head_ref; 
    } 
  
    // Function to check if a number is prime  
    static bool isPrime(int n) 
    { 
        // Corner cases  
        if (n <= 1)  
        { 
            return false; 
        } 
        if (n <= 3)  
        { 
            return true; 
        } 
  
        // This is checked so that we can skip  
        // middle five numbers in below loop  
        if (n % 2 == 0 || n % 3 == 0)  
        { 
            return false; 
        } 
  
        for (int i = 5; i * i <= n; i = i + 6)  
        { 
            if (n % i == 0 || n % (i + 2) == 0) 
            { 
                return false; 
            } 
        } 
        return true; 
    } 
  
    // function to delete all non-prime nodes  
    // from the singly linked list  
    static Node deleteNonPrimeNodes(Node head_ref)  
    { 
        // Remove all composite nodes 
        // at the beginning  
        Node ptr = head_ref; 
        while (ptr != null && !isPrime(ptr.data)) 
        { 
            Node temp = ptr; 
            ptr = ptr.next; 
        } 
        head_ref = ptr; 
        if (ptr == null)  
        { 
            return null; 
        } 
  
        // Remove remaining nodes  
        Node curr = ptr.next; 
        while (curr != null)  
        { 
            if (!isPrime(curr.data)) 
            { 
                ptr.next = curr.next; 
                curr = ptr.next; 
            }  
            else 
            { 
                ptr = curr; 
                curr = curr.next; 
            } 
        } 
        return head_ref; 
    } 
  
    // function to print nodes in a  
    // given singly linked list  
    static void printList(Node head) 
    { 
        while (head != null)  
        { 
            Console.Write(head.data + " "); 
            head = head.next; 
        } 
    } 
  
    // Driver code  
    public static void Main(String[] args)  
    { 
        // start with the empty list  
        Node head = null; 
  
        // create the linked list  
        // 15 . 16 . 7 . 6 . 17  
        head = push(head, 17); 
        head = push(head, 7); 
        head = push(head, 6); 
        head = push(head, 16); 
        head = push(head, 15); 
  
        Console.Write("Original List: "); 
        printList(head); 
  
        head = deleteNonPrimeNodes(head); 
  
        Console.Write("\nModified List: "); 
        printList(head); 
    } 
}  
  
// This code is contributed by 29AjayKumar 

Output:

Original List: 15 16 6 7 17 
Modified List: 7 17

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My Personal Notes

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

C++

Java

Python3

C#

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