Ruby在一个函数中从新创建的数组中获取最大值

Question

I want my function to return the longest Array within a nested array (including the array itself) so

nested_ary = [[1,2],[[1,2,[[1,2,3,4,[5],6,7,11]]]],[1,[2]]
deep_max(nested_ary)
 => [1,2,3,4,[5],6,7,11]

simple_ary = [1,2,3,4,5]
deep_max(simple_ary)
 => returns: [1,2,3,4,5]

I created a function to collect all arrays. I have to get the max value in another function.

my code:

def deep_max(ary)
  ary.inject([ary]) { |memo, elem|
  if elem.is_a?(Array)
    memo.concat(deep_max(elem))
  else
    memo
  end }
end

This gives me what I want:

deep_max(nested_ary).max_by{ |elem| elem.size }

Is there a way to get this max inside of the function?

Answer 1

You can unroll it:

def deep_max(ary)
  arys = []
  ary = [ary]
  until ary.empty?
    elem = ary.pop
    if elem.is_a?(Array)
      ary.push(*elem)
      arys.push(elem)
    end
  end
  arys.max_by(&:size)
end

Or you can cheat, by introducing an optional parameter that changes how your recursion works on top level vs how it behaves down the rabbit hole.

Answer 2

def deep_max(arr)
  biggest_so_far = arr
  arr.each do |e|
    if e.is_a?(Array)
      candidate = deep_max(e)
      biggest_so_far = candidate if candidate.size > biggest_so_far.size
    end
  end
  biggest_so_far
end

deep_max [[1, 2], [[1, 2, [[1, 2, 3, 4, [5], 6, 7, 11]]]], [1, [2]]]
  #=> [1, 2, 3, 4, [5], 6, 7, 11]