ruby - Ruby 中用于具有重复元素的集合的交集和并集

Question

我们如何在 Ruby 中为重复元素的集合获取交集和并集。

# given the sets
a = ["A", "B", "B", "C", "D", "D"]
b = ["B", "C", "D", "D", "D", "E"]

# A union function that adds repetitions
union(a, b)
=> ["A", "B", "B", "C", "D", "D", "D", "E"]

# An intersection function that adds repetitions
intersection(a, b)
=> ["B", "C", "D", "D"]

如文档中所写，& 和 | 运算符似乎会忽略重复和重复。

# union without duplicates
a | b
=> ["A", "B", "C", "D", "E"]

# intersections without duplicates
a & b
=> ["B", "C", "D"]

Answer 1

def union(a,b)
  (a|b).flat_map { |s| [s]*[a.count(s), b.count(s)].max }
end

union(a,b)
  # => ["A", "B", "B", "C", "D", "D", "D", "E"] 

def intersection(a,b)
  (a|b).flat_map { |s| [s]*[a.count(s), b.count(s)].min }
end

intersection(a,b)
  #=> ["B", "C", "D", "D"]