Class: Bwt

Inherits:
Object
  • Object
show all
Defined in:
lib/bwt.rb

Overview

Initial implementation of BWT algorithm

Burrows–Wheeler transform - block-sorting compression

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Bwt

Returns a new instance of Bwt.



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# File 'lib/bwt.rb', line 8

def initialize;end

Class Method Details

.bwt(string) ⇒ String

Transformation | - start flag. ~ - end flag.

Parameters:

  • String (String) —

    Any given string

Returns:

  • (String) —

    String transformed.



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# File 'lib/bwt.rb', line 14

def self.bwt(string)
  string2="|#{string}~"
  p string2
  len=string2.length
  m=[]
  (0...string2.length).collect { |i| (string2 * 2)[i, string2.length] }.each do |entry|
    arr=[]
    entry.split('').each do |letter|
      arr.push(letter)
    end
    m.push(arr)
  end
  a=m.sort
  b=[]
  a.each do |lt|
    b.push(lt[len-1])
  end
  return b.join('')
end

.bwt_rev(string) ⇒ Array

Inverse Transformation

Parameters:

  • String (String) —

    Inverse String

Returns:

  • (Array) —

    Array of letters - Original String



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# File 'lib/bwt.rb', line 37

def self.bwt_rev(string)
  len=string.length
  s1=""
  m=Array.new
  count = 0
  while count < len do
    if not m.any?
      string.split('').each do |s|
        s1=[s]
        m.push(s1)
        m.sort!
      end
      count += 1
    else
      val = 0
      string.split('').each do |s|
        m[val].insert(0,s)
        val += 1 
      end
      m.sort!
      count +=1
    end
  end
  m.each do |arr|
    if arr.last == "~"
      return arr
    end
  end
end