shinokada

grid = {0=>0, 1=>0, 2=>0, 3=>0, 4=>0, 5=>1, 6=>0, 7=>0, 8=>0, 9=>0, 10=>0, 11=>0, 12=>0, 13=>0, 14=>2, 15=>1, 16=>2, 17=>0, 18=>0, 19=>0, 20=>0, 21=>0, 22=>0, 23=>3, 24=>3, 25=>4, 26=>3, 27=>2, 28=>0, 29=>0, 30=>0, 31=>0, 32=>0, 33=>1, 34=>5, 35=>5, 36=>4, 37=>2, 38=>1, 39=>0, 40=>0, 41=>0, 42=>0, 43=>1, 44=>2, 45=>4, 46=>3, 47=>1, 48=>0, 49=>0, 50=>0, 51=>0, 52=>0, 53=>0, 54=>1, 55=>1, 56=>2, 57=>0, 58=>0, 59=>0, 60=>0, 61=>0, 62=>0, 63=>0, 64=>0, 65=>0, 66=>0, 67=>0, 68=>0, 69=>0, 70=>0, 71=>0, 72=>0, 73=>0, 74=>0, 75=>0, 76=>0, 77=>0, 78=>0, 79=>0, 80=>0, 81=>0, 82=>0, 83=>0, 84=>0, 85=>0, 86=>0, 87=>0, 88=>0, 89=>0, 90=>0, 91=>0, 92=>0, 93=>0, 94=>0, 95=>0, 96=>0, 97=>0, 98=>0, 99=>0}
gridcount = grid.values.inject(Hash.new(0)){|m,n| m[n] += 1;m }

p gridcount # return {0=>77, 1=>8, 2=>6, 3=>4, 4=>3, 5=>2}

shinokada

arr = [1, 1, 1, 2, 3]
freq = arr.inject(Hash.new(0)) { |h,v| h[v] += 1; h }
#=> {1=>3, 2=>1, 3=>1}
arr.max_by { |v| freq[v] }
#=> 1

shinokada

# method 1
hash = [[:first_name, 'Shane'], [:last_name, 'Harvie']].inject({}) do |result, element|
  result[element.first] = element.last
  result
end

hash # => {:first_name=>"Shane", :last_name=>"Harvie"}

# method 2

shinokada

# method 1
class Array
  def cumulative_sum
    sum = 0
    self.map{|x| sum += x}
  end
end

p [1,2,3,4].cumulative_sum

shinokada

ROMAN_MAP = { 1 => "I",
              4 => "IV",
              5 => "V",
              9 => "IX",
              10 => "X",
              40 => "XL",
              50 => "L",
              90 => "XC",
              100 => "C",
              400 => "CD",

shinokada

a = [[1, 2, 'apple'], [2, 6, 'banana'], [3, 10, 'egg']]
for no, num, item in a
  p "Shopping list #{no}: #{num} #{item}"
end

shinokada

@data = [
  ["M"  , 1000],
  ["CM" , 900],
  ["D"  , 500],
  ["CD" , 400],
  ["C"  , 100],
  ["XC" ,  90],
  ["L"  ,  50],
  ["XL" ,  40],
  ["X"  ,  10],

shinokada

# strange splat
[*0..9]  # [1,2,3,4,5,6,7,8,9]

# http://endofline.wordpress.com/2011/01/21/the-strange-ruby-splat/
# splat creates an array
first, *list = [1,2,3,4]          # first= 1, list= [2,3,4]
*list, last  = [1,2,3,4]          # list= [1,2,3], last= 4
first, *center, last = [1,2,3,4]  # first= 1, center= [2,3], last=4

a = *"Hello"  #=> ["Hello"]

shinokada

[1,2,3,4].inject(:+) # 10
[1,2,3,4].inject:+   # 10

shinokada

#!/usr/bin/ruby
# http://zetcode.com/lang/rubytutorial/io/
$stdout = File.open "output.log", "a" # redirect a standard output to a log file.
puts "Ruby"
puts "Java"
$stdout.close
$stdout = STDOUT # Use predefined standard constant STDOUT to recreate the normal standard output
puts "Python"