Alarm.rb (#73)


#1

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    until
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  1. Enjoy!

Suggestion: A [QUIZ] in the subject of emails about the problem helps
everyone
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#!/usr/bin/env ruby -w

Stephen W. removed_email_address@domain.invalid

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


#2

Sorry about this message folks. It was a comical naming error. I
was testing one of the solutions and it triggered the quiz posting
software. :smiley:

James Edward G. II