# Delete all Non-Prime Nodes from a Singly Linked List in C++

In this tutorial, we are going to learn how to delete all prime nodes from a singly linked list.

Let's see the steps to solve the problem.

• Write struct with data and next pointer.

• Write a function to insert the node into the singly linked list.

• Initialize the singly linked list with dummy data.

• Iterate over the singly linked list. Find whether the current node data is prime or not.

• If the current data is not prime, then delete the node.

• Write a function to delete the node. Consider the following three cases while deleting the node.

• If the node is head node, then move the head to next node.

• If the node is middle node, then link the next node to the previous node

• If the node is end node, then remove the previous node link.

## Example

Let's see the code.

Live Demo

#include <bits/stdc++.h>
using namespace std;
struct Node {
int data;
Node* next;
};
void insertNode(Node** head_ref, int new_data) {
Node* new_node = new Node;
new_node->data = new_data;
}
bool isPrime(int n) {
if (n <= 1) {
return false;
}
if (n <= 3) {
return true;
}
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;
}
while (ptr != NULL && !isPrime(ptr->data)) {
Node *temp = ptr;
ptr = ptr->next;
delete(temp);
}
if (ptr == NULL) {
return;
}
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;
}
}
}
cout << head->data << " -> ";
}
}
int main() {
cout << "Linked List before deletion:" << endl;
cout << "\nLinked List after deletion:" << endl;
}

## Output

If you run the above code, then you will get the following result.

Linked List before deletion:
6 -> 5 -> 4 -> 3 -> 2 -> 1 ->
5 -> 3 -> 2 ->