hash

#include <iostream>
#include <list>
#include <ctime>
#include <fstream>
#include <string>
#include <vector>
using namespace std;

struct Car
{
    int num;
    string brand;
    string ownerName;
};

Car createCar(int num, string brand, string ownerName)
{
    Car c;
    c.num = num;
    c.brand = brand;
    c.ownerName = ownerName;
    return c;
}

class HashTable
{
    int size;
    int countOfNotes = 0;
    list<Car>* table;

public:
    HashTable(int size);
    int getCountOfNotes();
    void insertItem(Car c);
    string getItem(int key);
    void deleteItem(int key);
    int hashFunction(int key);
    void rehash();
    void displayHash();
    void readFile();
    void writeFile();
};

void HashTable::readFile() {
    int num;
    string brand, ownerName;
    ifstream in("file.txt");
    if (in.is_open())
    {
        while (in >> num >> brand >> ownerName)
        {
            insertItem(createCar(num, brand, ownerName));
        }
    }
    in.close();
}

void HashTable::writeFile() {
    ofstream out;
    out.open("file.txt");
    if (out.is_open())
    {
        for (int index = 0; index < size; index++) {
            for (Car c : table[index]) {
                string car = "";
                car = to_string(c.num) + " " + c.brand + " " + c.ownerName;
                out << car + "\n";
            }
        }
    }
}

HashTable::HashTable(int size)
{
    this->size = size;
    table = new list<Car>[size];
}

int HashTable::getCountOfNotes() {
    return countOfNotes;
}

void HashTable::insertItem(Car c)
{
    int index = hashFunction(c.num);
    table[index].push_back(c);

    countOfNotes++;

    if (countOfNotes / size > 0.75) {
        rehash();
    }
    writeFile();
}

string HashTable::getItem(int key)
{
    int index = hashFunction(key);

    list<Car>::iterator i;
    for (i = table[index].begin(); i != table[index].end(); i++) {
        if (i->num == key)
            return to_string(i->num) + " " + i->brand + " " + i->ownerName;
    }
}

void HashTable::deleteItem(int key)
{
    int index = hashFunction(key);

    list<Car>::iterator i;
    for (i = table[index].begin(); i != table[index].end(); i++) {
        if (i->num == key)
            break;
    }

    if (i != table[index].end())
        table[index].erase(i);

    countOfNotes--;
    writeFile();
}

int HashTable::hashFunction(int key)
{
    return key % size;
}

void HashTable::rehash() {
    HashTable newHT(size * 2);
    for (int i = 0; i < size; i++) {
        for (Car c : table[i]) {
            newHT.insertItem(c);
        }
    }
    size = size * 2;
    table = newHT.table;
}

void HashTable::displayHash() {
    cout << "HashTable now:" << endl;
    for (int i = 0; i < size; i++) {
        cout << i;
        for (Car c : table[i])
            cout << " --> " << c.num;
        cout << endl;
    }
    cout << endl;
}

void generateFile(int count) {
    ofstream out;
    out.open("file.txt");
    for (int i = 0; i < count; i++) {
        string car;
        Car c;
        c.num = rand() % 100000 + 10000;
        c.brand = char(rand() % 26 + 65);
        c.ownerName = char(rand() % 26 + 65);
        car = to_string(c.num) + " " + c.brand + " " + c.ownerName;
        if (out.is_open())
        {
            out << car + "\n";
        }
    }
}



int main()
{
    srand(time(0));
    generateFile(5);
    HashTable ht(10);
    ht.readFile();
    ht.displayHash();
    int key;
    cout << "Enter key to delete note: ";
    cin >> key;
    cout << endl;
    ht.deleteItem(key);
    ht.displayHash();
    cout << "Enter key to find note: ";
    cin >> key;
    cout << "You found this car: " + ht.getItem(key) << endl;
    cout << endl;
    int num;
    string brand, ownerName;
    cout << "Add new note" << endl;
    cout << "Enter num: ";
    cin >> num;
    cout << "Enter brand: ";
    cin >> brand;
    cout << "Enter owner's name: ";
    cin >> ownerName;
    cout << endl;
    ht.insertItem(createCar(num, brand, ownerName));
    ht.displayHash();
    cout << "Enter key to find note: ";
    cin >> key;
    cout << "You found this car: " + ht.getItem(key) << endl;
    cout << endl;
    return 0;
}