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#!/usr/bin/env ruby -w
#
# Stephen Waits <steve@waits.net>
#
class AlarmKeypad
# init a keypad, with length of security code, and the code's stop digits
def initialize(code_length = 4, stop_digits = [1,2,3])
# remember the length of the security code
@code_length = code_length
# and which digits cause a code to be checked
@stop_digits = stop_digits
# and reset our data structures to 0
clear
end
# reset keypad to initial state
def clear
# an array of each code and how many times it's been entered
@codes = Array.new(10**@code_length,0)
# last N+1 keypad button presses
@key_history = []
# total number of keypad button presses
@key_presses = 0
end
# press a single digit
def press(digit)
# add digit to key history
@key_history.shift while @key_history.size > @code_length
@key_history << digit
@key_presses += 1
# see if we just tested a code
if @stop_digits.include?(@key_history.last) and
@key_history.length > @code_length
@codes[@key_history[0,@code_length].join.to_i] += 1
end
end
# find out if every code had been tested
def fully_tested?
not @codes.include?(0)
end
# find out if an individual code has been tested
# NOTE: an actual keypad obviously doesn't offer this functionality;
# but, it's useful and convenient (and might save duplication)
def tested?(code)
@codes[code] > 0
end
# output a summary
def summarize
tested = @codes.select { |c| c > 0 }.size
tested_multiple = @codes.select { |c| c > 1 }.size
puts "Search space exhausted." if fully_tested?
puts "Tested #{tested} of #{@codes.size} codes " +
"in #{@key_presses} keystrokes."
puts "#{tested_multiple} codes were tested more than once."
end
end
if $0 == __FILE__
# a random button presser, 3 digit codes
a = AlarmKeypad.new(3)
a.press( rand(10) ) until a.fully_tested?
a.summarize
# sequential code entry, 4 digit codes
a = AlarmKeypad.new(4)
("0000".."9999").each do |c|
next if a.tested?(c.to_i)
c.split(//).each { |d| a.press(d.to_i) }
a.press(rand(3)+1)
end
a.summarize
# sequential code entry, 5 digit codes, only [1] as a stop digit
a = AlarmKeypad.new(5,[1])
("00000".."99999").each do |c|
next if a.tested?(c.to_i)
c.split(//).each { |d| a.press(d.to_i) }
a.press(1)
end
a.summarize
end
