Class: Partitions::SetPartitions

Inherits:
Object
  • Object
show all
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.



5
6
7
8
9
10
11
12
 
# File 'lib/partitions/set_partitions.rb', line 5

def initialize(n, p=nil)
  @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.



3
4
5
 
# File 'lib/partitions/set_partitions.rb', line 3

def size
  @size
end

Instance Method Details

#count ⇒ Object 



111
112
113
114
115
116
117
118
119
120
121
 
# File 'lib/partitions/set_partitions.rb', line 111

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

#each_partition {|@k.clone| ... } ⇒ Object

Yields:

  • (@k.clone) 


98
99
100
101
102
103
104
105
106
107
108
109
 
# File 'lib/partitions/set_partitions.rb', line 98

def each_partition
  unless block_given?
    raise ArgumentError, "Missing block"
  end
  reinitialize
  yield @k.clone
  (count - 1).times do
    partition = next_partition
    yield partition
  end
  reinitialize
end

#next_partition ⇒ Object 



14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 
# File 'lib/partitions/set_partitions.rb', line 14

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 



57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
 
# File 'lib/partitions/set_partitions.rb', line 57

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