Please Forward: Ruby Quiz Submission

ruby-talk
1

From: James Koppel <darmaniiii@yahoo.com>
Date: April 6, 2007 9:10:12 PM CDT
To: submission@rubyquiz.com, submission@rubyquiz.com
Subject: Please Forward: Ruby Quiz Submission

Here is my solution to RubyQuiz #119. It implements both the basic criteria and the extra credit.

require 'enumerator'

class InsertedOperatorExpression
  attr_accessor :value, :expression

  def initialize(numbers, operators, operatorPlacement)
    @numbers = numbers
    @operators = .fill(nil, 0, numbers.length - 1)
    operatorPlacement.each_index {|x| @operators[operatorPlacement] = operators}
    @expression = @numbers.zip(@operators).flatten.join
    @value = eval(@expression.gsub(/(\d)([+-\/*%^])/, '\1.0\2').gsub(/\^/,'**')) # first gsub needed to prevent integer division
  end

  def to_s
    @expression + "=" + @value.to_s
  end

  def hash #Needed for uniq
    @expression.hash
  end

  def eql?(other) #Needed for uniq
    @expression == other.expression
  end
end

def findExpression(nums, ops, target)
  opPlacements = allPlacements(ops.length, (0...(nums.length - 1)).to_a)
  allExpressions = opPlacements.map {|placement| InsertedOperatorExpression.new(nums,ops, placement)}.uniq
  allExpressions.each do |expression|
    puts "******************************" if expression.value == target
    puts expression
    puts "******************************" if expression.value == target
  end
  puts "%d possible equations tested" % allExpressions.length
end

def allPlacements(remaining, avail, already=)
  return [already] if remaining == 0
  avail.enum_for.inject() {|placements, spot|
      placements + allPlacements( remaining - 1, avail - [spot], already + [spot])}
end

puts "Enter number sequence"
nums = gets.chomp.split(//).map {|c| c.to_i}
puts "Enter allowable operators (+-*/%^)"
ops = gets.chomp.split(//).map {|c| c.to_sym}
puts "Enter target value"
target = gets.chomp.to_f
findExpression(nums, ops, target)

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