From: Devin Chalmers <devin.chalmers@...>
Date: 2006-06-29T08:20:00+09:00
Subject: [SOLUTION][QUIZ] pp Pascal (#84)

 Hello everyone! This is my first quiz submission.

I suppose it's a little verbose, but I feel it's clever enough. I do
the straightforward, plain-vanilla recursive building of the triangle
right from the Array constructor, which is kinda cool, then extend the
Array class to print it out. (The to_centered_spaced_string method
really only works on a fairly specific subset of 2D arrays,
unfortunately.)

And, thanks for the quizzes! I have enjoyed the past entries greatly.

Devin Chalmers

PS - sorry for the 81-char line. I hate it too. :)

==== pp_pascal.rb

#!/usr/local/bin/ruby

def pascal_cell(row, col)
  return 1 if col == 0 or col == row
  return pascal_cell(row - 1, col) + pascal_cell(row - 1, col - 1)
end

def pascal_array(depth)
  Array.new(depth) {|i| Array.new(i + 1){|j| pascal_cell(i, j)}}
end

class Array
  def to_centered_spaced_string
    cell_width = self.flatten.collect{|val| val.to_s.size}.max + 2
    row_width  = self.collect{|row| row.size}.max * cell_width
    rows = Array.new(self.size) do |i|
      self[i].collect{|item|item.to_s.center(cell_width)}.join.center(row_width)
    end
    return rows.join("\n")
  end
end

puts pascal_array(ARGV[0].to_i).to_centered_spaced_string