//ProjectEuler/Java/Problem19.java
//Matthew Ellison
// Created: 03-14-19
//Modified: 03-28-19
//What is the sum of the digits of 100!?
//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/JavaClasses
/*
	Copyright (C) 2019  Matthew Ellison

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/


import mattrixwv.Stopwatch;
import java.math.BigInteger;


public class Problem20{
	private static Integer TOP_NUM = 100;
	public static void main(String[] argv){
		Stopwatch timer = new Stopwatch();
		BigInteger num = new BigInteger("1");	//The number that is being generated
		Long sum = 0L;	//The sum of the digits of num

		//Start the timer
		timer.start();

		//Run through every number from 1 to 100 and multiply it by the current num to generate 100!
		for(Integer cnt = TOP_NUM;cnt > 1;--cnt){
			num = num.multiply(BigInteger.valueOf(cnt));
		}

		//Get a string of the number because it is easier to pull appart the individucal characters
		String numString = num.toString();
		//Run through every character in the string, convert it back to an integer and add it to the running sum
		for(Integer cnt = 0;cnt < numString.length();++cnt){
			Character temp = numString.charAt(cnt);
			sum += Integer.valueOf(temp.toString());
		}

		//Stop the timer
		timer.stop();

		//Print the results
		System.out.printf("%d! = %s\n", TOP_NUM, num.toString());
		System.out.printf("The sum of the digits is: %d\n", sum);
		System.out.println("It took " + timer.getStr() + " to run this algorithm");
	}
}

/* Restuls:
100! = 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
The sum of the digits is: 648
It took 2.667 milliseconds to run this algorithm
*/