Question

我有一个数组，想在所有元素之间插入一个新元素，就像join方法一样。例如，我有

[1, [], "333"]

我需要的是

[1, {}, [], {}, "333"]

注意在所有元素之间插入了一个新的空哈希。

编辑：目前我所拥有的是：

irb(main):028:0> a = [1, [], "333"]
=> [1, [], "333"]
irb(main):029:0> a = a.inject([]){|x, y| x << y; x << {}; x}
=> [1, {}, [], {}, "333", {}]
irb(main):030:0> a.pop
=> {}
irb(main):031:0> a
=> [1, {}, [], {}, "333"]
irb(main):032:0>

我想知道最好的方法。

Answer 1

[1, 2, 3].flat_map { |x| [x, :a] }[0...-1]
#=> [1, :a, 2, :a, 3]

仅供参考，该功能称为intersperse（至少在Haskell中）。

[更新]如果要避免切片（创建数组的副本）：

[1, 2, 3].flat_map { |x| [x, :a] }.tap(&:pop)
#=> [1, :a, 2, :a, 3]

Answer 2

另一个类似的解决方案使用#product：

[1, 2, 3].product([{}]).flatten(1)[0...-1]
# => [ 1, {}, 2, {}, 3 ]

Answer 3

a = [1,2,3]
h, *t = a
r = [h]
t.each do |e|
  r.push({}, e)
end
r #=> [1, {}, 2, {}, 3]

Answer 4

您可以执行以下操作：

a = [1, [], "333"]
new_a = a.collect {|e| [e, {}]}.flatten(1)
=> [1, {}, [], {}, "333", {}]

您需要执行.flatten(1)因为它会在没有它的情况下展平您的空白数组。

或者正如@David Grayson在评论中所说的那样，你可以做flat_map同样的事情。

a.flat_map {|e| [e, {}]}
=> [1, {}, [], {}, "333", {}]

如果不需要最后一个{}，

@tokland有正确的答案。您将切片从0返回到长度 - 1或[0..-1]。

Answer 5

一种方法是压缩另一个所需元素数组，然后用depth = 1压缩它：

> arr = [1, [], "333"]
> element = {}
> interspersed = arr.zip([element] * (arr.size - 1)).flatten(1).compact
> # [1, {}, [], {}, "333" ]

您可以扩展Array以使此行为更易于访问。

class Array
  def intersperse(elem)
    self.zip([elem] * (self.size - 1)).flatten(1).compact
  end
end

例如，

[43] pry（主要）＆gt; [1,2,3] .intersperse（＆＃39;一个＆＃39;）
=＆GT; [1，＆＃34; a＆＃34;，2，＆＃34; a＆＃34;，3]

Answer 6

irb(main):054:0* [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(1).flat_map {|e| e << "XXX"}[0...-1]
=> [1, "XXX", 2, "XXX", 3, "XXX", 4, "XXX", 5, "XXX", 6, "XXX", 7, "XXX", 8, "XXX", 9]
irb(main):055:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(2).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, "XXX", 3, 4, "XXX", 5, 6, "XXX", 7, 8, "XXX", 9]
irb(main):056:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(3).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, "XXX", 4, 5, 6, "XXX", 7, 8, 9]
irb(main):057:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(4).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, 4, "XXX", 5, 6, 7, 8, "XXX", 9]
irb(main):058:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(5).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, 4, 5, "XXX", 6, 7, 8, 9]
irb(main):059:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(6).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, 4, 5, 6, "XXX", 7, 8, 9]
irb(main):060:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(7).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, 4, 5, 6, 7, "XXX", 8, 9]
irb(main):061:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(8).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, 4, 5, 6, 7, 8, "XXX", 9]
irb(main):062:0> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_slice(9).flat_map {|e| e << "XXX"}[0...-1]
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]
irb(main):063:0>

Answer 7

另一个与Tokland相似的人：

xs.inject([]){|x,y| x << y << {}}[0...-1]

Answer 8

[1, 2, 3, 4, 5].inject { |memo, el| Array(memo) << {} << el }
#=> [1, {}, 2, {}, 3, {}, 4, {}, 5]

inject将使用第一个元素开头，因此您不需要乱用索引。

如何在Ruby数组的所有元素之间插入一个新元素？

8 个答案: