Added solution to problem 38

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2021-10-22 19:28:33 -04:00
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Problem38.lua Normal file
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--ProjectEuler/ProjectEulerLua/Problem38.lua
--Matthew Ellison
-- Created: 10-11-21
--Modified: 10-11-21
--What is the largest 1-9 pandigital number that can be formed as the concatenated product of an integer with 1, 2, ... n where n > 1
--All of my requires, unless otherwise listed, can be found at https://bitbucket.org/Mattrixwv/luaClasses
--[[
Copyright (C) 2021 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"
require "Algorithms"
--Setup the variables
local timer = Stopwatch:create();
local HIGHEST_POSSIBLE_NUM = 9999; --The highest number that needs to be checked for a 1-9 pandigital
local largestNum = 0; --The number passed to the executeFormula function that returns the largest pandigital
local pandigital = 0; --The largest pandigital number found
--Functions
--Take the number ad add its multiples to a string to return
local function executeFormula(num)
--Turn the current number into a string
local numStr = tostring(num);
numStr = numStr .. tostring(num * 2);
--Multiply the number and append the product to the string until you have one long enough
local cnt = 3;
while(#numStr < 9) do
numStr = numStr .. tostring(num * cnt);
cnt = cnt + 1;
end
return numStr;
end
--Start the timer
timer:start();
--Loop from 1 -> HIGHEST_POSSIBLE_NUM checking for pandigitals
for cnt = 1, HIGHEST_POSSIBLE_NUM do
--Get the string from the formula
local numStr = executeFormula(cnt);
local panNum = tonumber(numStr);
--If the number is pandigital save it as the highest number
if(isPandigital(numStr) and (panNum > pandigital)) then
largestNum = cnt;
pandigital = panNum;
end
end
--Stop the timer
timer:stop();
--Print the results
io.write("The largest appened product pandigital is " .. pandigital .. "\n");
io.write("It took " .. timer:getString() .. " to run this algorithm\n");
--[[ Results:
The largest appened product pandigital is 932718654
It took 14.555 milliseconds to run this algorithm
]]