查找并返回嵌套数组中最长的数组及其大小答案

【问题标题】：Find and return the longest array in a nested array with its size查找并返回嵌套数组中最长的数组及其大小
【发布时间】：2017-12-05 13:54:13
【问题描述】：

我想编写一个函数，它接收一个嵌套数组并返回最长数组的大小及其本身。

max_with_size([])                                      # [0, []]
max_with_size([2,3,4])                                 # [3, [2, 3, 4]]
max_with_size([1,[2,3,4]])                             # [3, [2, 3, 4]]
max_with_size([[5,[6],[7,8,9],10,11]])                 # [5, [5, [6], [7, 8, 9], 10, 11]]
max_with_size([[1,[2,3,4]],[[[5,[6],[7,8,9],10,11]]]]) # [5, [5, [6], [7, 8, 9], 10, 11]]

到目前为止，我已经得到了这个

def max_with_size (ary)
  max_size = ary.size
  max_ary = ary 
  ary.each { |elem|
    if elem.is_a? Array
      if elem.size > max_size
        max_size = max_with_size(elem)[0]
        max_ary = max_with_size(elem)[1]
      end
    end
  }
  [max_size, max_ary]
end

前 4 种情况很好，但第 5 种失败了，只提供了这种情况

max_with_size([[1,[2,3,4]],[[[5,[6],[7,8,9],10,11]]]]) # [2, [[1, [2, 3, 4]], [[[5, [6], [7, 8, 9], 10, 11]]]]]

我怎样才能达到想要的结果？

【问题讨论】：

标签： ruby algorithm recursion multidimensional-array

【解决方案1】：

以下代码应打印所需的结果。我用 Inline cmets 解释了代码。

#Initialize @max to empty array, @max is an array with two elements, like this: [max_array_size, max_array]
@max = []

def max_with_size(array)
  # when @max is empty or when array size is greater than what is store in @max, store array size and array contents in @max
  (@max = [array.size, array]) if @max.empty? || (@max[0] < array.size)

  #Iterate through each element in array
  array.each do |x|

   #Skip to next element if x is not an array
   next unless x.is_a? Array
   #Recursively find max of array x 
   max_with_size(x)
  end
  @max
end

【讨论】：

【解决方案2】：

代码

def max_arr(arr)
  [arr, *arr.each_with_object([]) {|e,a| a << max_arr(e) if e.is_a?(Array) && e.any?}].
  max_by(&:size)
end

示例

examples = [[],
            [2,3,4],
            [1,[2,3,4]],
            [[5,[6],[7,8,9],10,11]],
            [[1,[2,3,4]],[[[5,[6],[7,8,9],10,11]]]],
            [1, [2, [3, 4, [6, 7, 8, 9, 10], [11, 12]], 13]]]

examples.each do |arr|
  a = max_arr(arr)
  puts "\n#{arr}\n  \#=> #{a.size}, #{a}"
end·

[]
  #=> 0, []

[2, 3, 4]
  #=> 3, [2, 3, 4]

[1, [2, 3, 4]]
  #=> 3, [2, 3, 4]

[[5, [6], [7, 8, 9], 10, 11]]
  #=> 5, [5, [6], [7, 8, 9], 10, 11]

[[1, [2, 3, 4]], [[[5, [6], [7, 8, 9], 10, 11]]]]
  #=> 5, [5, [6], [7, 8, 9], 10, 11]

[1, [2, [3, 4, [6, 7, 8, 9, 10], [11, 12]], 13]]
  #=> 5, [6, 7, 8, 9, 10]

【讨论】：