How would you write a non-recursive algorithm to calculate factorials?

Question

How would you write a non-recursive algorithm to compute n!?

Answer 1

Non recursive factorial in Java. This solution is with custom iterator (to demonstrate iterator use :) ).

/** 
 * Non recursive factorial. Iterator version,
 */
package factiterator;

import java.math.BigInteger;
import java.util.Iterator;

public class FactIterator
{   
    public static void main(String[] args)
    {
        Iterable fact = new Iterable()
        {
            @Override
            public Iterator iterator()
            {
                return new Iterator()
                {
                    BigInteger     i = BigInteger.ONE;
                    BigInteger total = BigInteger.ONE;

                    @Override
                    public boolean hasNext()
                    {
                        return true;
                    }

                    @Override
                    public BigInteger next()
                    {                        
                        total = total.multiply(i);
                        i = i.add(BigInteger.ONE);
                        return total;
                    }

                    @Override
                    public void remove()
                    {
                        throw new UnsupportedOperationException();
                    }
                };
            }
        };
        int i = 1;
        for (BigInteger f : fact)
        {
            System.out.format("%d! is %s%n", i++, f);
        }
    }
}