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Partitioning or Classifying a Set | ||
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Code | Expected | Actual |
require 'set' s = Set.new((1..10).collect) |
#<Set: {5, 6, 1, 7, 2, 8, 3, 9, 4, 10}> | #<Set: {5, 6, 1, 7, 2, 8, 3, 9, 4, 10}> |
s.divide { |x| x < 5 } |
#<Set: {#<Set: {5, 6, 7, 8, 9, 10}>, #<Set: {1, 2, 3, 4}>}> | #<Set: {#<Set: {5, 6, 7, 8, 9, 10}>, #<Set: {1, 2, 3, 4}>}> |
s.divide { |x| x % 2 } |
#<Set: {#<Set: {6, 2, 8, 4, 10}>, #<Set: {5, 1, 7, 3, 9}>}> | #<Set: {#<Set: {5, 1, 7, 3, 9}>, #<Set: {6, 2, 8, 4, 10}>}> |
s = Set.new([1, 2, 3, 'a', 'b', 'c', -1.0, -2.0, -3.0]) |
Divide the set into the "String subset, the "Fixnum" subset, and the "Float" subset. |
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s.divide { |x| x.class } |
#<Set: {#<Set: {"a", "b", "c"}>, | #<Set: {#<Set: {"a", "b", "c"}>, #<Set: {1, 2, 3}>, #<Set: {-1.0, -3.0, -2.0}>}> |
s = [1, 2, 3, -1, -2, -4].to_set |
Divide the set into sets of numbers with the same absolute value. |
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s.divide { |x,y| x.abs == y.abs } |
#<Set: {#<Set: {-1, 1}>, | #<Set: {#<Set: {-2, 2}>, #<Set: {-1, 1}>, #<Set: {3}>, #<Set: {-4}>}> |
s.divide { |x,y| (x-y).abs == 1 } |
#<Set: {#<Set: {1, 2, 3}>, | #<Set: {#<Set: {-2, -1}>, #<Set: {-4}>, #<Set: {1, 2, 3}>}> |
s.classify { |x| x.class } |
{String=>#<Set: {"a", "b", "c"}>, | {Fixnum=>#<Set: {-2, 1, -1, 2, 3, -4}>} |
connections = { 1 => 2, 2 => 3, 3 => 1, 4 => 1 } [1,2,3,4].to_set.divide { |x,y| connections[x] == y } |
#<Set: {#<Set: {1, 2, 3}>, #<Set: {4}>}> | #<Set: {#<Set: {1, 2, 3}>, #<Set: {4}>}> |
class Array def classify require 'set' h = {} each do |i| x = yield(i) (h[x] ||= self.class.new) << i end h end def divide(&block) Set.new(classify(&block).values) end end [1,1,2,6,6,7,101].divide { |x| x % 2 } |
#<Set: {[2, 6, 6], [1, 1, 7, 101]}> | #<Set: {[2, 6, 6], [1, 1, 7, 101]}> |
class Array def divide(&block) if block.arity == 2 counts = inject({}) { |h, x| h[x] ||= 0; h[x] += 1; h} to_set.divide(&block).inject([]) do |divided, set| divided << set.inject([]) do |partition, e| counts[e].times { partition << e } partition end end else Set.new(classify(&block).values) end end end [1,1,2,6,6,7,101].divide { |x,y| (x-y).abs == 1 } |
[[101], [1, 1, 2], [6, 6, 7]] | [[6, 6, 7], [101], [1, 1, 2]] |