рекурсия

#include <iostream>

using namespace std;

long long factor(int n) {
    cout << "call " << n << endl;
    if (n <= 1)
        return 1;
    return n * factor(n - 1);
}

long long factor2(int n) {
    long long res = 1;
    while (n > 1)
        res *= n--;
    return res;
}

void show(int size, int arr[]) {
    if (size == 0)
        return;
    cout << arr[0] << " ";
    show(size - 1, arr+1);
}

void show2(int size, int arr[]) {
    if (size == 0)
        return;
    show(size - 1, arr);
    cout << arr[size - 1] << " ";
}

int get_pow(int x, int y) {
    if (y == 0)
        return 1;
    return x * get_pow(x, y - 1);
}

int fibo(int n) {
    if (n < 2)
        return 1;
    return fibo(n - 1) + fibo(n - 2);
}

int fibo2(int n) {
    if (n < 2)
        return 1;
    int f_pred = 1;
    int f_pred_pred = 1;
    int f = 1;

    for (int k = 1; k < n; k++) {
        f = f_pred + f_pred_pred;
        f_pred_pred = f_pred;
        f_pred = f;
    }
    return f;
}


void test_recursion() {
    cout << "5! = " << factor(5) << endl;
    cout << "5! = " << factor2(5) << endl;

    const int size = 5;
    int arr[size]{ 501, 502, 503, 504, 505 };
    show(size, arr);
    cout << endl;
    show2(size, arr);
    cout << endl;

    cout << get_pow(3, 4) << endl;
    //3*3*3*3 = 9 * 9 = 81

    for (int n = 1; n < 20; n++) {
        cout << (double)fibo(n) / fibo(n-1) << " ";
    }
    cout << endl;

    for (int n = 0; n < 20; n++) {
        cout << fibo2(n) << " ";
    }
    cout << endl;
}

int main() {
    test_recursion();
    return 0;
}