将数组拆分为切片，并进行分组

Question

我这里有一些 Ruby 代码，可以工作，但我确定我没有尽可能高效地完成它。

我有一个对象数组，沿着这条线：

[
    { name: "foo1", location: "new york" },
    { name: "foo2", location: "new york" },
    { name: "foo3", location: "new york" },
    { name: "bar1", location: "new york" },
    { name: "bar2", location: "new york" },
    { name: "bar3", location: "new york" },
    { name: "baz1", location: "chicago" },
    { name: "baz2", location: "chicago" },
    { name: "baz3", location: "chicago" },
    { name: "quux1", location: "chicago" },
    { name: "quux2", location: "chicago" },
    { name: "quux3", location: "chicago" }
]

我想创建一些组 - 比如 3 - 每个组包含半等量的项目，但穿插 location。

我试过这样的事情：

group_size = 3
groups = []

group_size.times do
    groups.push([])
end

i = 0
objects.each do |object|
    groups[i].push(object)
    if i < (group_size - 1)
        i += 1
    else
        i = 0
    end
end

这个 returns 一个 groups 对象，看起来像：

[
    [{:name=>"foo1", :location=>"new york"},
     {:name=>"bar1", :location=>"new york"},
     {:name=>"baz1", :location=>"chicago"},
     {:name=>"quux1", :location=>"chicago"}],
    [{:name=>"foo2", :location=>"new york"},
     {:name=>"bar2", :location=>"new york"},
     {:name=>"baz2", :location=>"chicago"},
     {:name=>"quux2", :location=>"chicago"}],
    [{:name=>"foo3", :location=>"new york"},
     {:name=>"bar3", :location=>"new york"},
     {:name=>"baz3", :location=>"chicago"},
     {:name=>"quux3", :location=>"chicago"}]
]

因此您可以看到每个分组中的每个位置都有几个对象。

我试过 each_slice() 和 group_by()，甚至尝试使用 inject([]) - 但我想不出更优雅的方法来做到这一点。

我希望这是我忽略的东西 - 我需要考虑更多 location 和非偶数的对象。

Answer 1

a.each_slice(group_size).to_a.transpose

如果示例中准确描述了您的数据，则可以使用。如果不是，请提供准确的数据，以便我们更恰当地回答问题。

例如

a= [
    { name: "foo1", location: "new york" },
    { name: "foo2", location: "new york" },
    { name: "foo3", location: "new york" },
    { name: "bar1", location: "new york" },
    { name: "bar2", location: "new york" },
    { name: "bar3", location: "new york" },
    { name: "baz1", location: "chicago" },
    { name: "baz2", location: "chicago" },
    { name: "baz3", location: "chicago" },
    { name: "quux1", location: "chicago" },
    { name: "quux2", location: "chicago" },
    { name: "quux3", location: "chicago" }
]
group_size = 3
a.each_slice(group_size).to_a.transpose
#=> [
     [
      {:name=>"foo1", :location=>"new york"},
      {:name=>"bar1", :location=>"new york"},
      {:name=>"baz1", :location=>"chicago"},
      {:name=>"quux1", :location=>"chicago"}
    ],
    [
      {:name=>"foo2", :location=>"new york"},
      {:name=>"bar2", :location=>"new york"},
      {:name=>"baz2", :location=>"chicago"},
      {:name=>"quux2", :location=>"chicago"}
    ],
    [
      {:name=>"foo3", :location=>"new york"},
      {:name=>"bar3", :location=>"new york"},
      {:name=>"baz3", :location=>"chicago"},
      {:name=>"quux3", :location=>"chicago"}
    ]
  ]

在您的示例中，

each_slice 3 会将其分成 4 个相等的组（编号为 1、2、3）。 transpose然后将这4组变成3组4个。

如果位置不一定按顺序可以在方法链的前面添加排序

a.sort_by { |h| h[:location]  }.each_slice(group_size).to_a.transpose

更新

有人指出 transpose 的论点数量是奇数。我的第一个想法是采用@CarySwoveland 的方法，但由于他已经发布了它，所以我想出了一些不同的方法

class Array
  def indifferent_transpose
    arr = self.map(&:dup)
    max = arr.map(&:size).max
    arr.each {|a| a.push(*([nil] * (max - a.size)))}
    arr.transpose.map(&:compact)
  end
end

那么您仍然可以使用相同的方法

a << {name: "foobar1", location: "taiwan" }
a.each_slice(group_size).to_a.indifferent_transpose
#=> [[{:name=>"foo1", :location=>"new york"},
      {:name=>"bar1", :location=>"new york"},
      {:name=>"baz1", :location=>"chicago"},
      {:name=>"quux1", :location=>"chicago"},
      #note the extras values will be placed in the group arrays in order 
      {:name=>"foobar4", :location=>"taiwan"}], 
    [{:name=>"foo2", :location=>"new york"},
      {:name=>"bar2", :location=>"new york"},
      {:name=>"baz2", :location=>"chicago"},
      {:name=>"quux2", :location=>"chicago"}],
    [{:name=>"foo3", :location=>"new york"},
      {:name=>"bar3", :location=>"new york"},
      {:name=>"baz3", :location=>"chicago"},
      {:name=>"quux3", :location=>"chicago"}]]

Answer 2

是的，与 i 的这种记账通常表明应该有更好的东西。我想到了：

ar =[
    { name: "foo1", location: "new york" },
    { name: "foo2", location: "new york" },
    { name: "foo3", location: "new york" },
    { name: "bar1", location: "new york" },
    { name: "bar2", location: "new york" },
    { name: "bar3", location: "new york" },
    { name: "baz1", location: "chicago" },
    { name: "baz2", location: "chicago" },
    { name: "baz3", location: "chicago" },
    { name: "quux1", location: "chicago" },
    { name: "quux2", location: "chicago" },
    { name: "quux3", location: "chicago" }
]

# next line handles unsorted arrays, irrelevant with this data 
ar = ar.sort_by{|h| h[:location]}

num_groups = 3
groups     = Array.new(num_groups){[]}
wheel      = groups.cycle
ar.each{|h| wheel.next << h}

# done.
p groups
# => [[{:name=>"baz1", :location=>"chicago"}, {:name=>"quux1", :location=>"chicago"}, {:name=>"foo1", :location=>"new york"}, ...]

因为我喜欢 cycle 方法。

Answer 3

这是另一种方法。

代码

def group_em(a, ngroups)
  a.each_with_index.with_object(Array.new(ngroups) {[]}) {|(e,i),arr|
    arr[i%ngroups] << e}
end

例子

a = [
    { name: "foo1",  location: "new york" },
    { name: "foo2",  location: "new york" },
    { name: "foo3",  location: "new york" },
    { name: "bar1",  location: "new york" },
    { name: "bar2",  location: "new york" },
    { name: "bar3",  location: "new york" },
    { name: "baz1",  location: "chicago"  },
    { name: "baz2",  location: "chicago"  },
    { name: "baz3",  location: "chicago"  },
    { name: "quux1", location: "chicago"  },
    { name: "quux2", location: "chicago"  }
]

请注意，我从问题中省略了 a 的最后一个元素，以便 a 具有奇数个元素。

group_em(a,3)
  #=> [[{:name=>"foo1",  :location=>"new york"},
  #     {:name=>"bar1",  :location=>"new york"},
  #     {:name=>"baz1",  :location=>"chicago" },
  #     {:name=>"quux1", :location=>"chicago" }],
  #    [{:name=>"foo2",  :location=>"new york"},
  #     {:name=>"bar2",  :location=>"new york"},
  #     {:name=>"baz2",  :location=>"chicago" },
  #     {:name=>"quux2", :location=>"chicago" }],
  #    [{:name=>"foo3",  :location=>"new york"},
  #     {:name=>"bar3",  :location=>"new york"},
  #     {:name=>"baz3",  :location=>"chicago" }]]

将数组拆分为切片，并进行分组

Split an array into slices, with groupings

arrays

ruby

enumerable