Question

I have an array of 10 items and I want to split it up into 3 sections that look like this:

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

Using each_slice I can get close:

a = *(1..10)
a.each_slice(4) # use 4 so I can fit everything into 3 sections

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

But I want the first format which is more evenly distributed. I can do it writing my own method. But is there a built in way to do this in ruby 1.9+?

Update:

Since there’s no built in way I’d like to change my question to – how would you implement it?

Answer 1

Here’s my implementation

  def chunk(a, pieces)
     size = a.size / pieces
     extra = a.size % pieces
     chunks = []
     start = 0

     1.upto(pieces) do |i|
       last = (i <= extra) ? size.next : size
       chunks << a.slice(start, last)
       start = chunks.flatten.size
     end

     chunks
   end

call it like so

a = *(1..10)
puts chunk(a, 3)

will output

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

If piece size is too big it pads with empty arrays

a = *(1..10)
puts chunk(a, 14)

will output

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