Question

Please take a look at the below code

def test
  array = Array.new
  array2 = Array.new

  groups = [[424235, "goa", "italy"], [523436, "mumbai"], [342423, "africa", "goa"]]
  type = ["goa", "mumbai"]
  groups.each_with_index do |item,index|

       if item.include?(type[0]) == true
         array << index  << array2
        elsif item.include?(type[1]) == true
               array2 << index 
       else
         "nothing ;)"
       end

  end
  print array.each_slice(2).map { |a, b| [a, b.first] }
end
combine

#Output - [[0, 1], [2, 1]]

See the problem with the code? That is I am using a bunch of if and else statements. What if type array has more than 2 entries. I cant go on writing the if and elsif statements. And thats where I need your help. What is a better what to structure the code? loops? if so how.

Answer 1

Here is my code.

def combinations(groups, types)
  array = Array.new(types.size) { Array.new([]) }
  groups.each_with_index do |item, index|
     types.each_with_index { |type, i| array[i] << index if item.include? type }
  end

  flat = array.inject { |acc, i| acc.product i }.flatten
  flat.each_slice(types.size).to_a
end

Sample test cases

combinations([[424235, "goa", "italy"], [523436, "mumbai"], [342423, "africa", "goa"]], ["goa", "mumbai"])

output : [[0, 1], [2, 1]]

combinations([[424235, "goa", "italy"], [523436, "mumbai"], [342423, "africa", "goa"]], ["goa", "africa"])

output : [[0, 2], [2, 2]]

combinations([[424235, "goa", "italy"], [523436, "mumbai"], [342423, "africa", "goa"], [123, "india"]], ["goa", "mumbai", "india"])

output : [[0, 1, 3], [2, 1, 3]]

combinations([[424235, "goa", "italy"], [523436, "mumbai"], [342423, "mumbai", "goa"], [123, "india"]], ["goa", "mumbai", "india", "italy"])

output : [[0, 1, 3, 0], [0, 2, 3, 0], [2, 1, 3, 0], [2, 2, 3, 0]]

If I understood your problem correctly then these should be correct. Though I might have misunderstood you. Please do tell me If i have got your problem wrong, and If you could provide test cases that would be great.