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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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Problem3.m
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@@ -1,10 +1,11 @@
function [] = Problem3
%ProjectEuler/Octave/Problem3.m
%Matthew Ellison
% Created:
%Modified: 03-28-19
% Created: 03-28-19
%Modified: 10-28-20
%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
it under the terms of the GNU Lesser General Public License as published by
@@ -21,63 +22,28 @@
%}
%Setup your variables
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
tempNum = number; %Used to track the current value if all of the factors were taken out of number
%Setup your variables
number = 600851475143; %The number we are trying to find the greatest prime factor of
factors = []; %For the list of factors of number
%Get the prime numbers up to sqrt(number). If it is not prime there must be a value <= sqrt
primeNums = primes(sqrt(number));
%Get the prime numbers up to sqrt(number). If it is not prime there must be a value <= sqrt
primeNums = primes(sqrt(number));
%Start the timer
startTime = clock();
%Start the timer
startTime = clock();
%Setup the loop
counter = 1;
factors = factor(600851475143);
%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))
%Stop the timer
endTime = clock();
%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
%Print the results
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))
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
endTime = clock();
%Print the results
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))
%Cleanup your variables
clear counter;
clear tempNum;
clear answer;
clear number;
clear primeNums;
clear factors;
clear startTime;
clear endTime;
clear ans;
%{
Results:
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
%}