224: Recursions

1. Calculate base ^ pow through recursions:

#include <iostream>
using namespace std;
int power(int base, int pow)
{
    if (pow == 0)
    {
        return 1;
    }

    int prevAns = power(base, pow - 1);
    return base * prevAns;
}

int main()
{
    int base = 2;
    int pow = 5;
    cout << base << '^' << pow << ": " << power(base, pow) << endl;
}

/*
2 * 2 * 2 * 2 * 2
base ^ pow = base * (base ^ power - 1)
*/

 




































2: Calculate factorial through recursion:

#include <iostream>
using namespace std;
int factorial(int num)
{
    if (num == 1)
    {
        return 1;
    }

    int prev = factorial(num - 1);
    return num * prev;
    // or return num * factorial(num - 1)
}

int main()
{
    int num = 5;
    cout << num << "!: " << factorial(num) << endl;

    return 0;
}

// 5! = 5 * 4 * 3 * 2 * 1
// num! = num * (num - 1)!

3. Write a program to print n number of fibonacci sequence numbers:

In this program, we are printing every fibonacci number and returning the last fibonacci number so that it can be printed when returned to the main.

#include <iostream>
using namespace std;
int fibonacci(int target, int term1 = 0, int term2 = 1)
{
    cout << term1 << " ";
    if (target == 0)
    {
        return term1 + term2;
    }
    else
    {
       return fibonacci(target - 1, term2, term1 + term2);
    }
}

int main()
{
    cout << "Fibonacci Series: " << fibonacci(5);
    return 0;
}

























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