euler14

gistfile1.rb

#!/usr/bin/env ruby
require 'benchmark'

def collatzSequence(x) # e.g. 916
    n = x
    chain = 0
    loop do 
        if n % 2 == 0
            n = n/2
            chain = chain + 1
        else
            n = 3 * n + 1
            chain = chain + 1
        end
        break if n == 1
    end
    return chain + 1
end 

def doTest()
#start from 1m and work backwards?
count = 1_000_000
record = 0 #the biggest chain so far...
loop do
    c = collatzSequence(count)
    if c > record
        c = record
    end
    count = count - 1
end
end

puts Benchmark.measure { doTest() }