package rebelsky.arrays;

/**
* An assistant that knows how to do some basic computations
* with arrays.
*
* @author Samuel A. Rebelsky
* @version 1.0 of October 2004
*/
public class Computer
{
	/**
	 * Sum all the cache in stuff.
	 */
	public double sum(double[] stuff) {
		// Prepare to total the cache
		double total = 0;     
		// Step through the array, adding each value
		for(int i = 0; i < stuff.length; i = i + 1) {
			total = total + stuff[i];
		}
		// Return the total value
		return total;
	} // sum

	/**
	 * Compute the nth Fibonacci number recursively.
	 */
	public long fibr(int n)
	{
		if (n < 2)
			return n;
		else
			return fibr(n-1) + fibr(n-2);
	} // fibr(int)

	/**
	 * Compute the nth Fibonacci number recursively,
	 * using an array.
	 */
	public long fibra(int n)
	{
		long[] cache = new long[n+1];
		cache[0] = 0;
		cache[1] = 1;
		for (int i = 2; i <= n; i++)
			cache[i] = -1;
		return fibra_helper(n, cache);
	} // fibra(int)

	public long fibra_helper(int n, long[] cache)
	{
		if (cache[n] == -1)
			cache[n] = fibra_helper(n-1, cache)
				+ fibra_helper(n-2, cache);
		return cache[n];
	} // fibra_helper

} // class Computer