Oki_HappyNumbers_Newton

// ConsoleApplication3.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include "pch.h"
#include <iostream>
#include <string>
#include <random>
#include <conio.h>

using namespace std;

void generate(int *, int&);
void happyNumbers(int *, int);
void sets(int*, int, int*, int*);
void print(int *, int);

/*! C(n, k) = C(n - 1, k - 1) + C(n - 1, k) */
/*! C(n, 0) = C(n, n) = 1 */
/*! C(12, 2) = 11 1 + 11 2, 10 - 0 10 1 = 66 */
int newtonBinomial(int n, int k) {
    if (k == 0  || k < 0|| k == n)
        return 1;

    return newtonBinomial(n - 1, k - 1) + newtonBinomial(n - 1, k);
}


int main()
{

    int lotteryNumbers[100];
    int distinct[100], axioation[100];
    int choice, lotteryNumbersSize;

    do {

        system("cls");

        cout << "1. Generate\n";
        cout << "2. Happy Numbers\n";
        cout << "3. Sets\n";
        cout << "4. Print\n";
        cout << "5. Newton's Binomial Coefficient\n\n";

        cout << "0. Exit\n\n";

        cout << "Your choice: ";
        cin >> choice;

        switch (choice) {
        case 1:

            system("cls");

            generate(lotteryNumbers, lotteryNumbersSize);

            cout << "\n\nPress any key to get back to the menu..";
            _getch();
            break;

        case 2:

            system("cls");

            happyNumbers(lotteryNumbers, lotteryNumbersSize);

            cout << "\n\nPress any key to get back to the menu..";
            _getch();
            break;

        case 3:

            system("cls");

            sets(lotteryNumbers, lotteryNumbersSize, distinct, axioation);

            cout << "\n\nPress any key to get back to the menu..";
            _getch();
            break;

        case 4:

            system("cls");

            print(lotteryNumbers, lotteryNumbersSize);

            cout << "\n\nPress any key to get back to the menu..";
            _getch();
            break;

        case 5: {

            system("cls");

            int n, k;

            cout << "This is a combination of C(n, k) = C(n - 1, k - 1) + C(n - 1, k)\n\n";

            cout << "Enter n: ";
            cin >> n;

            cout << "Enter k: ";
            cin >> k;

            int coefficient = newtonBinomial(n, k);

            cout << "\n\nNewton's Binomial Coefficient is " << coefficient;

            cout << "\n\nPress any key to get back to the menu..";
            _getch();
            break;
            }
        }
    } while (choice != 0);
}

void generate(int *array, int& array_size)
{
    random_device rd;
    mt19937 gen(rd());
    uniform_int_distribution<> dist(100000, 999999);
    uniform_int_distribution<> arrSize(50, 100);

    array_size = arrSize(gen);

    for (int i = 0; i < array_size; i++) {
        array[i] = dist(gen);
    }

    cout << "Numbers generated!\n";
}

void happyNumbers(int *array, int size) {

    cout << "Happy Numbers:\n\n";

    int counter = 0;

    for (int i = 0; i < size; i++) {
        string firstNumbers(to_string(array[i]).substr(0, 3));
        string lastNumbers(to_string(array[i]).substr(3, 3));

        int firstSum = 0, lastSum = 0;

        for (int i = 0; i < firstNumbers.length(); i++) {
            firstSum += firstNumbers[i] - 48;

            //cout << fistSum[i] << " -- ";
        }

        for (int i = 0; i < lastNumbers.length(); i++) {
            lastSum += lastNumbers[i] - 48;

            //cout << lastSum[i] << " -- ";
        }

        if (firstSum == lastSum) {
            counter++;
            cout << "Number:  " << array[i] << "  - First Numbers sum: " << firstSum << " - Last Numbers sum: " << lastSum << endl;
        }
    }

    if (counter == 0)
        cout << "There are no happy numbers!";
}

void sets(int *array, int size, int *arr1, int *arr2) {
    for (int i = 0; i < size; i++) {
        if (((i >> 2) << 2) == i && (i & 1))
            arr1[i] = i;

        if (((i >> 2) << 2) == i)
            arr2[i] = i;
        else if (i & 1)
            arr2[i] = i;
    }

    cout << "Sets have been copied to two new arrays!";
}

void print(int * array, int size) {
    for (int i = 0; i < size; i++) {
        if (((i >> 2) << 2) == i)
            cout << endl;

        cout << array[i] << "  ";
    }
}