--ProjectEuler/lua/Problem1.lua
--Matthew Ellison
-- Created: 02-01-19
--Modified: 03-28-19
--The sum of the even Fibonacci numbers less than 4,000,000
--All of my requires, unless otherwise listed, can be found at https://bitbucket.org/Mattrixwv/luaClasses
--[[
	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/>.
]]


require "Stopwatch"


timer = Stopwatch:create();
timer:start();

--Setup the variables
TOP_NUM = 4000000;	--The highest looked for Fibonacci numbers
fibSum = 0;		--Holds the sum of the Fibonacci numbers
fibNums = {1, 1, 2};	--An array to keep track of the Fibonacci numbers

--Loop to generate the Fibonacci numbers
cnt = 2;	--A counter to hold the location in the array of the currently working Fibonacci number
fibNums[(cnt % 3) + 1] = fibNums[((cnt - 1) % 3) + 1] + fibNums[((cnt - 2) % 3) + 1];
while(fibNums[(cnt % 3) + 1] < TOP_NUM) do
	--If the number is even add it to the sum, otherwise ignore it
	if((fibNums[(cnt % 3) + 1] % 2) == 0) then
		fibSum = fibSum + fibNums[(cnt % 3) + 1];
	end
	--Generate the next Fibonacci number in the sequence
	cnt = cnt + 1
	fibNums[(cnt % 3) + 1] = fibNums[((cnt - 1) % 3) + 1] + fibNums[((cnt - 2) % 3) + 1];
end

timer:stop();

--Print the results
print("The sum of all even Fibonacci numbers less than " .. TOP_NUM .. " is " .. fibSum);
print("It took " .. timer:getMicroseconds() .. " microseconds to run this algorithm");


--[[Results:
The sum of all even Fibonacci numbers less than 4000000 is 4613732
It took 56 microseconds to run this algorithm
]]