Count of Prime Nodes of a Singly Linked List

Given a singly linked list containing N nodes, the task is to find the total count of prime numbers.

Examples:

Input: List = 15 -> 5 -> 6 -> 10 -> 17
Output: 2
5 and 17 are the prime nodes

Input: List = 29 -> 3 -> 4 -> 2 -> 9
Output: 3
2, 3 and 29 are the prime nodes

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

Approach: The idea is to traverse the linked list to the end and check if the current node is prime or not. If YES, increment the count by 1 and keep doing the same until all the nodes get traversed.

Below is the implementation of above approach:

C++

// C++ implementation to find count of prime numbers 
// in 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 find count of prime 
// nodes in a linked list 
int countPrime(Node** head_ref) 
{ 
    int count = 0; 
    Node* ptr = *head_ref; 
  
    while (ptr != NULL) { 
        // If current node is prime 
        if (isPrime(ptr->data)) { 
            // Update count 
            count++; 
        } 
        ptr = ptr->next; 
    } 
  
    return count; 
} 
  
// Driver program 
int main() 
{ 
    // start with the empty list 
    Node* head = NULL; 
  
    // create the linked list 
    // 15 -> 5 -> 6 -> 10 -> 17 
    push(&head, 17); 
    push(&head, 10); 
    push(&head, 6); 
    push(&head, 5); 
    push(&head, 15); 
  
    // Function call to print require answer 
    cout << "Count of prime nodes = "
         << countPrime(&head); 
  
    return 0; 
} 

Java

// Java implementation to find count of prime numbers  
// in the singly linked list  
class solution 
{ 
  
// 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 find count of prime  
// nodes in a linked list  
static int countPrime(Node   head_ref)  
{  
    int count = 0;  
    Node  ptr =  head_ref;  
  
    while (ptr != null) {  
        // If current node is prime  
        if (isPrime(ptr.data)) {  
            // Update count  
            count++;  
        }  
        ptr = ptr.next;  
    }  
  
    return count;  
}  
  
// Driver program  
public static void main(String args[]) 
{  
    // start with the empty list  
    Node  head = null;  
  
    // create the linked list  
    // 15 . 5 . 6 . 10 . 17  
    head=push(head, 17);  
    head=push(head, 10);  
    head=push(head, 6);  
    head=push(head, 5);  
    head=push(head, 15);  
  
    // Function call to print require answer  
    System.out.print( "Count of prime nodes = "+ countPrime(head));  
  
}  
} 
  
// This code is contributed by Arnab Kundu 

Python3

# Python3 implementation to find count of  
# prime numbers in the singly linked list 
  
# 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
      
    i = 5
    while i * i <= n:  
        if n % i == 0 or n % (i + 2) == 0:  
            return False
        i += 6
  
    return True
  
# Link list node 
class Node:  
      
    def __init__(self, data, next): 
        self.data = data 
        self.next = next
          
class LinkedList: 
      
    def __init__(self): 
        self.head = None
      
    # Push a new node on the front of the list.      
    def push(self, new_data): 
        new_node = Node(new_data, self.head) 
        self.head = new_node 
  
    # Function to find count of prime  
    # nodes in a linked list  
    def countPrime(self):  
      
        count = 0
        ptr = self.head  
      
        while ptr != None:  
              
            # If current node is prime  
            if isPrime(ptr.data):  
                  
                # Update count  
                count += 1
              
            ptr = ptr.next
      
        return count  
  
# Driver Code 
if __name__ == "__main__": 
  
    # Start with the empty list 
    linkedlist = LinkedList() 
  
    # create the linked list  
    # 15 -> 5 -> 6 -> 10 -> 17  
    linkedlist.push(17)  
    linkedlist.push(10)  
    linkedlist.push(6)  
    linkedlist.push(5)  
    linkedlist.push(15)  
  
    # Function call to print require answer  
    print("Count of prime nodes =", 
           linkedlist.countPrime())  
  
# This code is contributed by Rituraj Jain 

C#

// C# implementation to find count of prime numbers  
// in 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 find count of prime  
// nodes in a linked list  
static int countPrime(Node head_ref)  
{  
    int count = 0;  
    Node ptr = head_ref;  
  
    while (ptr != null)  
    {  
        // If current node is prime  
        if (isPrime(ptr.data))  
        {  
            // Update count  
            count++;  
        }  
        ptr = ptr.next;  
    }  
  
    return count;  
}  
  
// Driver code  
public static void Main(String []args) 
{  
    // start with the empty list  
    Node head = null;  
  
    // create the linked list  
    // 15 . 5 . 6 . 10 . 17  
    head=push(head, 17);  
    head=push(head, 10);  
    head=push(head, 6);  
    head=push(head, 5);  
    head=push(head, 15);  
  
    // Function call to print require answer  
    Console.Write( "Count of prime nodes = "+ countPrime(head));  
}  
} 
  
// This code has been contributed by 29AjayKumar 

Output:

Count of prime nodes = 2

Time Complexity: O(N*sqrt(P)), where N is length of the LinkedList and P is the maximum element in the List

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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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