#include <iostream>
#include <string>
using namespace std;

//Recursion!

//rule for today:  no loops.


void blastOff(int n)
{
	if (n==0)  //Base case: when is problem super easy
	{
		cout << "B L A S T O F F!!!!" << endl;
	}
	else   //Recursive case: problem is big and hard, use recursion!
	{
		cout << n << " ";
		blastOff(n - 1);
	}
}

//Return sum of 1+2+...+n
int sum(int n)
{
	if (n==1) //Base case
	{
		return 1;
	}
	else //Recursive case
	{
		int subsum = sum(n - 1);
		return n + subsum;
	}
}

int factorial(int n)
{
	if (n==1) //Base case
	{
		return 1;
	}
	else  //Recursive case
	{
		return n * factorial(n - 1);
	}
}

//Return sum of items array from index start to end.
//Assume start<=end
double sumArray(double * items, int start, int end)
{
	if (start == end) //Base case
	{
		return items[start];
	}
	else  //Recursive case
	{
		return items[start] + sumArray(items, start + 1, end);
	}
}

int main()
{
	blastOff(10);  //10 9 8 7 ... 3 2 1 BLASTOFF!
	cout << endl << endl;
	blastOff(100);

	//Challenge #1
	int x = sum(20); //add up 1+2+3+...+20
	cout << x << endl;

	//Challenge #2
	cout << factorial(5) << endl; //5*4*3*2*1

	//Challenge #3:
	double nums[] = { 17.8, 3.14, 21, 43, 8, 2.1, 41, 13.7, 8.3 };
	cout << sumArray(nums, 0, 8);

	//Challenge #4:
	//cout << power(3, 4) << endl;

	//Challenge #5: compute nth fibonacci number
	//cout << fib(9) << endl;

	return 0;
}