Question

I can’t seem to find an algorithm to compute the number of arrays within an array. Example

Given

[ [ "Array", "1" ], [ "Array", "2" ] ]

Output should be two

Given

[
    [
        [ ["Array", "1"], ["Array", "2"] ],
        [ ["Array", "3"], ["Array", "4"] ],
    ],
    [
        [ ["Array", "5"], ["Array", "6"] ],
        [ ["Array", "7"], ["Array", "8"] ]
    ]
]`

Output should be 8

Answer 1

This recursive function will do the job for arrays of any nesting:

def count_subarrays array
  return 0 unless array && array.is_a?(Array)

  nested = array.select { |e| e.is_a?(Array) }
  if nested.empty?
    1 # this is a leaf
  else
    nested.inject(0) { |sum, ary| sum + count_subarrays(ary) }
  end
end