ruby - 数组的所有可能分布，来自一个数字

Question

我不太确定如何表达这一点，所以我只是举个例子。

如果我写:

some_method(["a", "b"], 3)

我希望它返回某种形式的

[{"a" => 0, "b" => 3},
 {"a" => 1, "b" => 2},
 {"a" => 2, "b" => 1},
 {"a" => 3, "b" => 0}]

如果我传入

some_method(%w(a b c), 2)

期望的返回值应该是

[{"a" => 2, "b" => 0, "c" => 0},
 {"a" => 1, "b" => 1, "c" => 0},
 {"a" => 1, "b" => 0, "c" => 1},
 {"a" => 0, "b" => 2, "c" => 0},
 {"a" => 0, "b" => 1, "c" => 1},
 {"a" => 0, "b" => 0, "c" => 2}]

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描述这个很难，所以如果您回答这个问题，请提前致谢!

Answer 1

这是一种方法:

def some_method ary, num
 permutations = (0..num).to_a.repeated_permutation(ary.size).select do |ary| 
    ary.reduce(:+) == num 
 end

 return permutations.map { |a| (ary.zip a).to_h }
end

p some_method ["a", "b"], 3
#=> [{"a"=>0, "b"=>3}, {"a"=>1, "b"=>2}, {"a"=>2, "b"=>1}, {"a"=>3, "b"=>0}]
p some_method %w(a b c), 2
#=> [{"a"=>0, "b"=>0, "c"=>2}, {"a"=>0, "b"=>1, "c"=>1}, {"a"=>0, "b"=>2, "c"=>0}, {"a"=>1, "b"=>0, "c"=>1}, {"a"=>1, "b"=>1, "c"=>0}, {"a"=>2, "b"=>0, "c"=>0}]

根据@seph 的提示更新了答案