Class: ExactCover::MatrixPreprocessor

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

Overview

Transforms an array into a linked list of data and column objects

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(matrix) ⇒ MatrixPreprocessor

Returns a new instance of MatrixPreprocessor.



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# File 'lib/exact_cover/matrix_preprocessor.rb', line 8

def initialize(matrix)
  @matrix = matrix
  @row_count = matrix.size
  @col_count = matrix[0].size
end

Instance Attribute Details

#col_count ⇒ Object (readonly)

Returns the value of attribute col_count.



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# File 'lib/exact_cover/matrix_preprocessor.rb', line 6

def col_count
  @col_count
end

#matrix ⇒ Object (readonly)

Returns the value of attribute matrix.



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# File 'lib/exact_cover/matrix_preprocessor.rb', line 4

def matrix
  @matrix
end

#row_count ⇒ Object (readonly)

Returns the value of attribute row_count.



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# File 'lib/exact_cover/matrix_preprocessor.rb', line 5

def row_count
  @row_count
end

Instance Method Details

#call ⇒ Object 



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# File 'lib/exact_cover/matrix_preprocessor.rb', line 14

def call
  # Generates the column objects
  headers = []
  (0..col_count - 1).each do |col|
    col_size = size(col)
    headers[col] = ColumnObject.new(col_size, col.to_s)
  end

  # Fill the left and right for each header object
  prev = headers[-1]
  headers.each do |current|
    current.left = prev
    prev.right = current
    prev = current
  end

  # Generates the data objects (one for each 1 in the matrix)
  data_objects = []
  row_objects_array = []
  col_objects_array = []
  (0..row_count - 1).each do |row|
    data_objects[row] = []
    row_objects_array[row] = []
    (0..col_count - 1).each do |col|
      column = headers[col]
      col_objects_array[col] = [column] if col_objects_array[col].nil?
      next unless matrix[row][col] == 1

      data_object = DataObject.new(column)
      data_objects[row][col] = data_object
      row_objects_array[row] << data_object
      col_objects_array[col] << data_object
    end
  end

  # Fill the left and right fields
  row_objects_array.each do |row_objects|
    prev = row_objects[-1]
    loop do
      break if row_objects.empty?

      current = row_objects.shift
      current.left = prev
      prev.right = current
      prev = current
    end
  end

  # Fill the up and down fields
  col_objects_array.each do |col_objects|
    prev = col_objects[-1]
    loop do
      break if col_objects.empty?

      current = col_objects.shift
      current.up = prev
      prev.down = current
      prev = current
    end
  end

  # insert the root between headers[-1] and headers[0]
  root = ColumnObject.new(0, "root")
  headers[-1].right = root
  headers[0].left = root
  root.right = headers[0]
  root.left = headers[-1]

  root
end