1_weather.rb

def smallest_temperature_spread
  # store all munged values in a hash
  map = {}

  File.open("weather.dat", "r") do |file|
    # iterate each line
    while line = file.gets
      # only use relevant lines
      if line.match(/^\s+\d+\s+[\d\*]+\s+/)
        # seems appropriate to convert keys to integers here for possible future use
        day = line.split[0].to_i
        spread = (line.split[1].to_i-line.split[2].to_i).abs
        map[day] = spread
      end
    end
  end

  # sort the spread values, index 0 will be the smallest
  # there may be occasions when there are joint smallest spreads -
  # we could check for this with Hash#select and return an array instead
  smallest_spread = map.values.sort[0]
  smallest_spread_day = map.index(smallest_spread)

  puts "Minimum temperature spread was "+smallest_spread.to_s+", from day "+smallest_spread_day.to_s

  smallest_spread_day
end

2_football.rb

# not goal difference, strictly speaking, so let's call it spread again!
def smallest_goal_spread
  map = {}

  File.open("football.dat", "r") do |file|
    while line = file.gets
      if line.match(/^\s+[\d\.]+\s+/)
        map[line.split[1]] = (line.split[6].to_i - line.split[8].to_i).abs
      end
    end
  end

  goal_spread = map.values.sort[0]
  team_name = map.index(goal_spread)

  puts "Smallest spread between goals for and against was "+goal_spread.to_s+", by "+team_name

  team_name
end

3a_refactor.rb

module Spread

  # refactored to work with either file and to calculate spread on any two columns
  def smallest(file_path, columns = { :return => 0, :first => 0, :second => 1 })
    map = {}

    File.open(file_path, "r") do |file|
      while line = file.gets
        # this regexp works for both sets of data
        if line.match(/^\s+[\d\.]+\s+/)
          map[line.split[columns[:return]]] = (line.split[columns[:first]].to_i - line.split[columns[:second]].to_i).abs
        end
      end
    end

    spread = map.values.sort[0]
    return_value = map.index(spread)

    #puts "Smallest spread was "+spread.to_s+", from "+return_value

    return_value
  end

end

3b_refactor_test.rb

require '3a_refactor'
require 'test/unit'

class SpreadTest < Test::Unit::TestCase

  include Spread

  def test_smallest_temperature_spread
    assert_equal "14", smallest("weather.dat", { :return => 0, :first => 1, :second => 2 })
  end

  def test_smallest_football_goal_spread
    assert_equal "Aston_Villa", smallest("football.dat", { :return => 1, :first => 6, :second => 8 })
  end

end