main.rb

#!/usr/bin/env ruby
# generates a matrix and display groups (blobs) in the matrix
# without arguments, generates a 5 * 5 matrix
#   usage: blobs.rb [cols] [rows]

# example
#   generated:
#   [0, 0, 1, 0, 1]
#   [0, 0, 0, 0, 1]
#   [0, 0, 0, 0, 1]
#   [0, 1, 1, 0, 1]
#   [1, 0, 1, 0, 1]
#   
#   grouped:
#   [0, 0, 2, 0, 3]
#   [0, 0, 0, 0, 3]
#   [0, 0, 0, 0, 3]
#   [0, 4, 4, 0, 3]
#   [5, 0, 4, 0, 3]

# generate an n * m length array of 1's and 0's in random order
def generate_matrix(m,n)
  Array.new(m*n) {|i| rand.round }
end

# returns a matrix with each group numbered
def find_blobs(matrix, m, n)
  group = 2

  matrix.each_index do |index|
    if matrix[index] == 1
      matrix = find_neighbors(matrix, m, n, index, group)

      group = group + 1
    end
  end

  return matrix
end

# recursively look on all "sides" of the index'th element in search of neighbors
# neighbors are elements that equal 1, everything else is ignored
def find_neighbors(matrix, m, n, index, group)
  return matrix if matrix[index] == 0 or index >= matrix.size

  matrix[index] = group

  # top
  unless index - m < 0 or matrix[index - m] == group
    matrix = find_neighbors(matrix, m, n, index - m, group)
  end

  # bottom
  unless index + m > m * n or matrix[index + m] == group
    matrix = find_neighbors(matrix, m, n, index + m, group)
  end

  # left
  unless index % m == 0 or index == 0
    matrix = find_neighbors(matrix, m, n, index - 1, group) unless matrix[index - 1] == group
  end

  # right
  unless index % m == m - 1 or index == m * n
    matrix = find_neighbors(matrix, m, n, index + 1, group) unless matrix[index + 1] == group
  end

  return matrix
end

def main
  m = ARGV[0].to_i
  n = ARGV[1].to_i

  m = 5 if m == 0
  n = 5 if n == 0

  puts "generated:"
  matrix = generate_matrix(m, n)
  matrix.each_slice(m) {|a| p a}

  puts "\ngrouped:"
  matrix = find_blobs(matrix, m, n)
  matrix.each_slice(m) {|a| p a}
end

main