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# Count of Prime Nodes of a Singly Linked List

• Difficulty Level : Basic
• Last Updated : 28 May, 2021

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
```

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 ``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`

## Javascript

 ``
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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