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92 lines
2.3 KiB
Lua
92 lines
2.3 KiB
Lua
--ProjectEuler/lua/Problem23.lua
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--Matthew Ellison
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-- Created: 03-22-19
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--Modified: 06-19-20
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--Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers
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--All of my requires, unless otherwise listed, can be found at https://bitbucket.org/Mattrixwv/luaClasses
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--[[
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Copyright (C) 2020 Matthew Ellison
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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]]
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require "Stopwatch"
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require "Algorithms"
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MAX_NUM = 28123; --The highest number that will be evaluated
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local function isSum(abund, num)
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local sumOfNums = 0;
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--Pick a number for the first part of the sum
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for firstNum = 1, #abund do
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for secondNum = firstNum, #abund do
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sumOfNums = abund[firstNum] + abund[secondNum];
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if(sumOfNums == num) then
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return true;
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elseif(sumOfNums > num) then
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break;
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end
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end
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end
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return false;
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end
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--Setup the variables
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local timer = Stopwatch:create();
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local divisorSums = {};
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--Start the timer
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timer:start();
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--Get the sum of the divisors of all numbers < MAX_NUM
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for cnt = 1, MAX_NUM do
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local div = getDivisors(cnt);
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if(#div > 1) then
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table.remove(div, #div);
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end
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divisorSums[cnt] = getSum(div);
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end
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--Get the abundant numbers
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local abund = {};
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for cnt = 1, #divisorSums do
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if(divisorSums[cnt] > cnt) then
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abund[#abund + 1] = cnt;
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end
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end
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--Check if each number can be the sum of 2 abundant numbers and add to the sum if no
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local sumOfNums = 0;
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for cnt = 1, MAX_NUM do
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if(not isSum(abund, cnt)) then
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sumOfNums = sumOfNums + cnt;
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end
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end
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--Stop the timer
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timer:stop();
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--Print the results
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io.write("The answer is " .. sumOfNums .. '\n');
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io.write("It took " .. timer:getSeconds() .. " seconds to run this algorithm\n");
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--[[Results:
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The answer is 4179871
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It took 393.139 seconds to run this algorithm
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]]
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