如何将红宝石中的阵列切成指定长度的子阵列？

Question

I'd like to split an array into sub arrays of a specified length.

I know that .each_slice will chunk an array into equal length subarrays with the remainder leftover like so:

a = [1,2,3,4,5,6,7,8,9,10]
a.each_slice(3).to_a => [[1,2,3],[4,5,6],[7,8,9],[10]]

However, say I want the output like this:

=> [[1],[2,3],[4,5,6],[7,8,9,10]]

Is there a method in ruby for slicing an array into different specified lengths depending on the arguments you give it?

Answer 1

Try this

a = [1,2,3,4,5,6,7,8,9,10]
slices = [1,2,3,4].map { |n| a.shift(n) }

This slices the array into pieces

NB, this mutates the original array.

Answer 2

I cannot see how to improve on @akuhn's answer, but here are a couple of other methods that could be used.

a = [1,2,3,4,5,6,7,8,9,10,11]
slice_sizes = [1,2,3,4]

#1 Stab out slices

def variable_slice(a, slice_sizes)
  last = 0
  slice_sizes.each_with_object([]) do |n,arr|
    arr << a[last,n]
    last += n
  end
end

variable_slice(a, slice_sizes)
  #=> [[1], [2, 3], [4, 5, 6], [7, 8, 9, 10]]

#2 Use recursion

def variable_slice(a, slice_sizes)
  return [] if slice_sizes.empty?
  i, *rest = slice_sizes
  [a.first(i)].concat variable_slice(a[i..-1], rest)
end

variable_slice(a, slice_sizes)
  #=> [[1], [2, 3], [4, 5, 6], [7, 8, 9, 10]]