Ruby Program/Problem

Question

Given a string of characters as input, without using regular expression or pattern matching, how to get the output, if the characters matches aaa should output 1 and if the characters matches aBa should output 2. (Note: Should not re-process characters so as to output both “1” and “2” when processing the same input)

So for example:

given 'aaBaBaaaBaaa' it should output 211

given 'aaaBaBaaaaBBaBaBa' it should output 1212

Thanks in advance.

Answer 1

without using regular expression or pattern matching

#input = 'aaBaBaaaBaaa'
input = 'aaaBaBaaaaBBaBaBa'
codes = {'aaa' => 1, 'aBa' => 2}
patterns = codes.keys
output = []

current = 0
length = input.length

while current <= length - 1
    is_find = false
    patterns.each do|pattern|
        len = pattern.length
        if input[current, len] == pattern
            output << codes[pattern]
            current += len
            is_find = true
            break
        end
    end

    current += 1 if !is_find
end

p output

Answer 2

Sounds like you want a state machine:

require 'statemachine'

state_machine = Statemachine.build do
  trans :_, :a, :a
  trans :_, :B, :_
  trans :a, :a, :aa
  trans :a, :B, :aB
  trans :aa, :a, :_, 'print 1'
  trans :aa, :B, :aB
  trans :aB, :a, :_, 'print 2'
  trans :aB, :B, :_
end

"aaBaBaaaBaaa".each_char do |i|
  state_machine.process_event(i)
end

state_machine.reset
puts

"aaaBaBaaaaBBaBaBa".each_char do |i|
  state_machine.process_event(i)
end