Compare multidimensional arrays in Ruby and show result array with existing and missed items-CodePudding

You have a 2-dimensional array of strings:

[
    ["AAA", "BBB", "CCC", "DDD"],
    ["BBB", "CCC", "DDD"],
    ["AAA", "CCC", "DDD"],
    ["AAA", "CCC", "DDD", "EEE"]
]

You need to compare each subarray with other subarrays to get result as a 2-dimensional array which will show whether each string present in the current subarray and in other subarrays or not (if not - it should be nil) like this (RESULT):

[
    ["AAA", nil, "AAA", "AAA"], 
    ["BBB", "BBB", nil, nil], 
    ["CCC", "CCC", "CCC", "CCC"], 
    ["DDD", "DDD", "DDD", "DDD"], 
    [nil, nil, nil, "EEE"]
]

How to write a function that takes an initial array and returns array like in the RESULT example?

CodePudding user response：

if list has the next values:

list = [
        ["AAA", "BBB", "CCC", "DDD"],
        ["BBB", "CCC", "DDD"],
        ["AAA", "CCC", "DDD"],
        ["AAA", "CCC", "DDD", "EEE"]
    ]

then

def method_name(list)
  handled_list = list.flatten.uniq
  handled_list.each_with_object([]) do |item, res|
    res << list.map{ |sub_array| sub_array.find{ |s| s == item } }
  end
end

CodePudding user response：

arr = [
    ["AAA", "BBB", "CCC", "DDD"],
    ["BBB", "CCC", "DDD"],
    ["AAA", "CCC", "DDD"],
    ["AAA", "CCC", "DDD", "EEE"]
]

all = arr.reduce(:|)
  #=> ["AAA", "BBB", "CCC", "DDD", "EEE"]
arr.map { |row| all.map { |s| row.include?(s) ? s : nil } }.transpose
  #=> [["AAA",   nil, "AAA", "AAA"],
  #    ["BBB", "BBB",   nil,   nil],
  #    ["CCC", "CCC", "CCC", "CCC"],
  #    ["DDD", "DDD", "DDD", "DDD"],
  #    [  nil,   nil,   nil, "EEE"]]

See Array#| (array union) for calculating all.

transpose's receiver equals

arr.map { |row| all.map { |s| row.include?(s) ? s : nil } }
  #=> [["AAA", "BBB", "CCC", "DDD",  nil],
  #    [  nil, "BBB", "CCC", "DDD",  nil],
  #    ["AAA",   nil, "CCC", "DDD",  nil],
  #    ["AAA",   nil, "CCC", "DDD", "EEE"]]