[Ruby] On Euler 14

2008-04-06T00:19:24-07:00

slightly faster, caches more data

require 'benchmark' 

def operation(n)
  return n%2 == 0 ? n/2 : 3*n+1 
end

def recursive(hash, n)
  hash[n] or hash[n] = 1 + recursive(hash, operation(n) )
end

chains = {} 
max_chain_size = 0 
max_chain_start = 1 

Benchmark.bm do |x| 
  x.report do 
    chains[1] = 1
    2.upto(1000000) do |i| 
      chain_size = recursive(chains, i)
      
      if chain_size > max_chain_size 
        max_chain_size = chain_size 
        max_chain_start = i 
      end 
    end 
  end 
  puts "(#{max_chain_start}, #{max_chain_size})" 
end

[Ruby] On Recursive Hash#fetch

2008-03-21T00:20:02-07:00

well, since we're already reopening standard classes, I thought it might make sense to move the Array logic into class Array. Now we have simple recursion of methods, instead of having to make private functions.

class Hash
  def fetch_all(key)
    return [] if not self.has_key?(key)
    value = self.fetch(key)
    [ value ] + [ value ].fetch_all(key)
  end
end

class Array
  def fetch_all(key)
    self.find_all{|x| x.respond_to? :fetch_all} \
      .map{|x| x.fetch_all(key) } \
      .inject( [] ){|a,b| a + b }
  end
end

jes5199

[Ruby] On Euler 14

[Ruby] On Recursive Hash#fetch