Add two polynomials using linked list in C++

addTwoPolynomials.cpp

#include <iostream>
using namespace std;

class Node {
public:
  int coeff;
  int power;
  Node *next;
};

void create_node(int x, int y, Node **temp) {
  Node *a, *r;
  a = *temp;
  if (a == NULL) {
    r = new Node;
    r->coeff = x;
    r->power = y;
    *temp = r;
    r->next = new Node;
    r = r->next;
    r->next = NULL;
  } else {
    r->coeff = x;
    r->power = y;
    r->next = new Node;
    r = r->next;
    r->next = NULL;
  }
}

void add(Node *p1, Node *p2, Node *result) {
  while (p1->next && p2->next) {
    if (p1->power > p2->power) {
      result->power = p1->power;
      result->coeff = p1->coeff;
      p1 = p1->next;
    } else if (p1->power < p2->power) {
      result->power = p2->power;
      result->coeff = p2->coeff;
      p2 = p2->next;
    } else {
      result->power = p1->power;
      result->coeff = p1->coeff + p2->coeff;
      p1 = p1->next;
      p2 = p2->next;
    }
    result->next = new Node;
    result = result->next;
    result->next = NULL;
  }
  while (p1->next || p2->next) {
    if (p1->next) {
      result->power = p1->power;
      result->coeff = p1->coeff;
      p1 = p1->next;
    }
    if (p2->next) {
      result->power = p2->power;
      result->coeff = p2->coeff;
      p2 = p2->next;
    }
    result->next = new Node;
    result = result->next;
    result->next = NULL;
  }
}

// display function to print resultant polynomial
void display(Node *node) {
  while (node->next != NULL) {
    cout << node->coeff << "x^" << node->power;
    node = node->next;
    if (node->next != NULL)
      cout << " + ";
  }
  cout << endl;
}

int main() {
  Node *p1 = NULL, *p2 = NULL, *result = NULL;
  // creating polynomial1 p1 and polynomial2 p2
  create_node(4, 5, &p1);
  create_node(2, 3, &p1);
  create_node(5, 0, &p1);
  create_node(2, 3, &p2);
  create_node(5, 2, &p2);
  create_node(5, 1, &p2);
  cout << "polynomial 1: ";
  display(p1);
  cout << endl << "polynomial 2: ";
  display(p2);
  result = new Node;
  add(p1, p2, result);
  cout << endl << "resultant polynomial: ";
  display(result);
  return 0;
}