Class: Partitions::SetPartitions

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/partitions/set_partitions.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(n, p = nil) ⇒ SetPartitions

Returns a new instance of SetPartitions.

Raises:

  • (ArgumentError) 


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# File 'lib/partitions/set_partitions.rb', line 6

def initialize(n, p = nil)
  raise ArgumentError, "n must be a non-negative Integer" unless n.is_a?(Integer) && n >= 0
  if !p.nil? && (!p.is_a?(Integer) || p < 1 || p > n)
    raise ArgumentError, "p must be an Integer between 1 and n"
  end

  @n = n
  @k = Array.new(n, 0)
  @m = Array.new(n, 0)
  @p = p
  pinitialize
  @size = partition_size
end

Instance Attribute Details

#size ⇒ Object

Returns the value of attribute size.



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# File 'lib/partitions/set_partitions.rb', line 4

def size
  @size
end

Instance Method Details

#count ⇒ Object 



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# File 'lib/partitions/set_partitions.rb', line 116

def count
  if @p.nil?
    sum = 0
    (1..n).each do |k|
      sum += sterling_second(@n, k)
    end
    sum
  else
    sterling_second(@n, @p)
  end
end

#each_partition {|@k.clone| ... } ⇒ Object Also known as: each

Yields:

  • (@k.clone) 


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# File 'lib/partitions/set_partitions.rb', line 104

def each_partition
  return enum_for(:each_partition) unless block_given?

  reinitialize
  yield @k.clone
  (count - 1).times do
    yield next_partition
  end
  reinitialize
end

#next_partition ⇒ Object 



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# File 'lib/partitions/set_partitions.rb', line 20

def next_partition
  if @p.nil?
    (@n - 1).downto(1) do |i|
      if @k[i] <= @m[i - 1]
        @k[i] = @k[i] + 1
        @m[i] = max(@m[i], @k[i])
        j = i + 1
        while j <= (n - 1) do
          @k[j] = @k[0]
          @m[j] = @m[i]
          j = j + 1
        end
        @size = partition_size
        return @k.clone
      end
    end
  else
    p = partition_size
    (@n - 1).downto(1) do |i|
      if (@k[i] < (p - 1)) && (@k[i] <= @m[i - 1])
        @k[i] = @k[i] + 1
        @m[i] = max(@m[i], @k[i])
        j = i + 1
        while j <= (@n - (p - @m[i])) do
          @k[j] = 0
          @m[j] = @m[i]
          j = j + 1
        end
        j = @n - (p - @m[i]) + 1
        while j <= (n - 1) do
          @k[j] = @m[j] = p - (@n - j)
          j = j + 1
        end
        @size = partition_size
        return @k.clone
      end
    end
  end

  @size = nil
  return 
end

#previous_partition ⇒ Object 



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# File 'lib/partitions/set_partitions.rb', line 63

def previous_partition
  if @p.nil?
    (@n - 1).downto(1) do |i|
      if @k[i] > @k[0]
        @k[i] = @k[i] - 1
        @m[i] = @m[i - 1]
        j = i + 1
        while j <= n - 1 do
          @k[j] = @m[j] = @m[i] + j - i;
          j = j + 1
        end
        @size = partition_size
        return @k.clone
      end
    end
  else
    p = partition_size
    (@n - 1).downto(1).each do |i|
      if (@k[i] > 0) && ((p - @m[i - 1]) <= (n - i))
        @k[i] = @k[i] - 1
        @m[i] = @m[i - 1]
        j = i + 1
        while j <= (i + (p - @m[i]) - 1) do
          @k[j] = @m[j] = @m[i] + j - i
          j = j + 1
        end
        j = i + (p - @m[i])
        while j <= (@n - 1) do
          @k[j] = @m[j] = p - 1
          j = j + 1
        end
        @size = partition_size
        return @k.clone
      end
    end
  end

  @size = nil
  return
end