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Updated problem 3 algorithm

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Mattrixwv
2020-10-29 08:43:06 -04:00
parent 57c3fa5b43
commit d8a77a9266
1 changed files with 18 additions and 52 deletions
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48
Problem3.m
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@@ -1,10 +1,11 @@
function [] = Problem3
%ProjectEuler/Octave/Problem3.m %ProjectEuler/Octave/Problem3.m
%Matthew Ellison %Matthew Ellison
% Created: % Created: 03-28-19
%Modified: 03-28-19 %Modified: 10-28-20
%The largest prime factor of 600851475143 %The largest prime factor of 600851475143
%{ %{
Copyright (C) 2019 Matthew Ellison Copyright (C) 2020 Matthew Ellison
This program is free software: you can redistribute it and/or modify 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 it under the terms of the GNU Lesser General Public License as published by
@@ -23,9 +24,7 @@
%Setup your variables %Setup your variables
number = 600851475143; %The number we are trying to find the greatest prime factor of number = 600851475143; %The number we are trying to find the greatest prime factor of
primeNums = []; %A list of prime numbers. Will include all prime numbers <= number
factors = []; %For the list of factors of number factors = []; %For the list of factors of number
tempNum = number; %Used to track the current value if all of the factors were taken out of number
%Get the prime numbers up to sqrt(number). If it is not prime there must be a value <= sqrt %Get the prime numbers up to sqrt(number). If it is not prime there must be a value <= sqrt
primeNums = primes(sqrt(number)); primeNums = primes(sqrt(number));
@@ -33,30 +32,7 @@ primeNums = primes(sqrt(number));
%Start the timer %Start the timer
startTime = clock(); startTime = clock();
%Setup the loop factors = factor(600851475143);
counter = 1;
%Start with the lowest number and work your way up. When you reach a number > size(primeNums) you have found all of the factors
while(counter <= size(primeNums)(2))
%Divide the number by the next prime number in the list
answer = (tempNum/primeNums(counter));
%If it is a whole number add it to the factors
if(mod(answer,1) == 0)
factors(end + 1) = primeNums(counter);
%Set tempNum so that it reflects number/factors
tempNum = tempNum / primeNums(counter);
%Keep the counter where it is in case a factor appears more than once
%Get the new set of prime numbers
primeNums = primes(sqrt(tempNum));
else
%If it was not an integer increment the counter
++counter;
end
end
%When the last number is not divisible by a prime number it must be a prime number
factors(end + 1) = tempNum;
%Stop the timer %Stop the timer
endTime = clock(); endTime = clock();
@@ -64,20 +40,10 @@ endTime = clock();
%Print the results %Print the results
printf("The largest prime factor of 600851475143 is %d\n", max(factors)) printf("The largest prime factor of 600851475143 is %d\n", max(factors))
printf("It took %f seconds to run this algorithm\n", etime(endTime, startTime)) printf("It took %f seconds to run this algorithm\n", etime(endTime, startTime))
end
%Cleanup your variables
clear counter;
clear tempNum;
clear answer;
clear number;
clear primeNums;
clear factors;
clear startTime;
clear endTime;
clear ans;
%{ %{
Results: Results:
The largest prime factor of 600851475143 is 6857 The largest prime factor of 600851475143 is 6857
It took 0.006256 seconds to run this algorithm It took 0.005714 seconds to run this algorithm
%} %}