Polynomial expression with Linked list

Polynomial expression with Linked list.cpp

#include <iostream>
#include <string>
#include <vector>
#include <sstream>

using namespace std;

struct node{
	int Coefficient_field;
	int Exponent_field;
	node *next;
};

class Node_d{
public:
	node *first, *temp;

	void add_last(){
		node *tempx = first;
		if (tempx != NULL)
		{
			while (tempx->next != NULL)
				tempx = tempx->next;

			tempx->next = temp;
		}
		else
			first = temp;
	}

	Node_d(){
		first = NULL;
	}

	void insert_n(int cf, int ef){
		temp = new node;
		temp->Coefficient_field = cf;
		temp->Exponent_field = ef;
		temp->next = NULL;
		add_last();
	}

	int length(){
		int count = 0;
		temp = first;
		while (temp != NULL){
			count++;
			temp = temp->next;
		}
		return count;
	}

	node *search(int ef)
	{
		node *tempx = first;
		while (tempx != NULL)
		{
			if (ef == tempx->Exponent_field)
				return tempx;
			else
				tempx = tempx->next;
		}
		return NULL;
	}

	void display(){
		node *tempx;
		tempx = first;
		string sign;

		if (tempx != NULL)
		{
			while (tempx->next != NULL){
				if (tempx == first)
					cout << "X^" << tempx->Exponent_field;
				else
				{
					if (tempx->Coefficient_field > 0)
						cout << " + " << tempx->Coefficient_field << "X^" << tempx->Exponent_field;
					else if (tempx->Coefficient_field < 0)
						cout << tempx->Coefficient_field << "X^" << tempx->Exponent_field;
				}
				tempx = tempx->next;
			}

			if (tempx->next == NULL)
			{
				if (tempx == first)
					cout << "X^" << tempx->Exponent_field;
				else
				{
					if (tempx->Coefficient_field > 0)
						cout << " + " << tempx->Coefficient_field << "X^" << tempx->Exponent_field;
					else if (tempx->Coefficient_field < 0)
						cout << tempx->Coefficient_field << "X^" << tempx->Exponent_field;
				}
			}
		}
		else
			cout << "there is no values" << endl;

	}
};

// Split Function
vector<string> split(string str, char delimiter) {
	vector<string> internal;
	stringstream ss(str); // Turn the string into a stream.
	string tok;

	while (getline(ss, tok, delimiter)) {
		internal.push_back(tok);
	}

	return internal;
}

void main(){
	string expression1, expression2;
	Node_d E1, E2, R;
	vector<string> after_split, next_split;

	cout << "Enter POLYNOMIAL EXPRESSION n.1 :";
	getline(cin, expression1);

	after_split = split(expression1, ' ');
	for (int i = 0; i < after_split.size(); i++)
	{
		next_split = split(after_split[i], ',');
		E1.insert_n(stoi(next_split[0]), stoi(next_split[1]));
	}

	cout << "Enter POLYNOMIAL EXPRESSION n.2 :";
	getline(cin, expression2);

	after_split = split(expression2, ' ');
	for (int i = 0; i < after_split.size(); i++)
	{
		next_split = split(after_split[i], ',');
		E2.insert_n(stoi(next_split[0]), stoi(next_split[1]));
	}

	node *search, *search_result;
	Node_d search_in;
	if (E1.length() >= E2.length())
	{
		search = E1.first;
		search_in = E2;
	}
	else
	{
		search = E2.first;
		search_in = E1;
	}
	while (search != NULL)
	{
		search_result = search_in.search(search->Exponent_field);

		if (search_result != NULL)
			R.insert_n(search->Coefficient_field + search_result->Coefficient_field, search->Exponent_field);
		else
			R.insert_n(search->Coefficient_field , search->Exponent_field);
		search = search->next;
	}

	cout << "Final result :";
	R.display();

	cin.get();
	cin.ignore();
}