I'm trying to re-write the prime factors kata without using the Prime
library. About to go berserk with frustration, too.
I've tried a mess of different techniques and puts'd all over the place
to "see" a solution, but have just been looking at it too long now.
Right now the code below will iterate over a range, find the factors,
and add
to array.
But I'm missing something to reduce the factors to actual prime factors.
: \
The following produces the answer I'm looking for, with the prime
library (for
guidance).
require 'prime'
def prime(n)
n.prime_division.map { |base, exp| [base]*exp }.flatten
end
Any input on the below?? Thanks in advance for your time & help
# -----------
# Create a method which takes integers and returns their prime factors
in an array.
# primes are integers greater than 1,
# divisible only by 1 and themselves.
# primes > 2 are odd numbers.
# prime factors of integer <= square root of integer parameter (n)
def primes(n)
puts
puts
# initialize the array to add the prime factors
prime_factors = []
factor = n
# iterate over range, up to sqrt integer
(2).upto(Math.sqrt(factor).to_i). each do |divisor|
# for divisor in (2..factor) do
# Math.sqrt(factor).to_i.downto(2).each do |divisor|
puts "Finding primes from #{divisor} to #{factor}."
puts
puts "Checking now if #{divisor} is a factor."
if factor % divisor == 0
puts "--> #{factor} is divisible by #{divisor}."
prime_factors << divisor
puts "Factors array now set: #{prime_factors.inspect}"
quotient = factor / divisor
factor = quotient
end #/if loop
end #/do
puts
puts "Exiting loop; #{factor} is the last quotient to've passed if
statement."
prime_factors << factor
p prime_factors
end
# primes(256) # should print [2,2,2,2,2,2,2,2]
# primes(100) # should print [2,2,5,5]
# primes(81) # should print [3,3,3,3]
# primes(10) # should print [2,5]
primes(8) # should print [2,2,2] --> currently prints [2,4]
···
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