Array of Arrays sum in ruby

Question

arry = [["a",3.0,3], ["b",4.0,4], ["c",5.0,5]]

I am looking for the following output

[["a", 3.0, [["b", 4.0, 7], ["c", 5.0, 8]]],
 ["b", 4.0, [["a", 3.0, 7], ["c", 5.0, 9]]],
 ["c", 5.0, [["a", 3.0, 8], ["b", 4.0, 9]]]]

This is what I have done

With the size of the array, I iterated over the loop
First, I have taken the first element.
Deleted it and made a new array. I iterated through the new array, calculated the sum and pushed the elements to new array2
I added the deleted element at the end

I am not able to produce the following above mentioned format of the output. The output I am able to do is

[a,3.0,b,4.0,7]
7 here is 3+4
[a,3.0,c,5.0,8]
[b,4.0,c,5.0,9]
..etc

Apart from that, how to code to display lets say only the elements less than 8

and get this output

[["a",3.0,["b",4.0,7]],["b",4.0,["a",5.0,7]],["c",5.0,[]]

What are the transformation rules (I don't see what your expected output means)? — Sergio Tulentsev
– Sergio Tulentsev, Commented Apr 26, 2013 at 23:34
@SergioTulentsev Looks like a mapping between an element and every other element and when a specific element is the key their value is added to others. — Hunter McMillen
– Hunter McMillen, Commented Apr 26, 2013 at 23:37
Neither of your outputs are valid - you're missing some ] somewhere — Frederick Cheung
– Frederick Cheung, Commented Apr 26, 2013 at 23:39
I have changed the output and corrected the ]. Thank you for pointing it out! — gkolan
– gkolan, Commented Apr 26, 2013 at 23:58

Darshan Rivka Whittle · Accepted Answer · 2013-04-27 01:00:28Z

1

arry.map do |inner|
  dup = inner.dup
  n = dup[2]
  dup[2] = []

  arry.each do |other|
    next if other == inner # Only want other inner arrays
    other_dup = other.dup
    other_dup[2] += n
    dup[2] << other_dup
  end

  dup
end

This evaluates to:

[["a", 3.0, [["b", 4.0, 7], ["c", 5.0, 8]]],
 ["b", 4.0, [["a", 3.0, 7], ["c", 5.0, 9]]],
 ["c", 5.0, [["a", 3.0, 8], ["b", 4.0, 9]]]]

Update: Glad that's what you wanted. This is ugly, but I think it satisfies your filtering goal:

mapped.map do |inner|
  inner_dup = inner.dup

  inner_dup[2] = inner_dup[2].select do |inner_inner|
    inner_inner[2] < 8  # Condition for the elements you want to test
  end

  inner_dup
end

This evaluates to:

[["a", 3.0, [["b", 4.0, 7]]], ["b", 4.0, [["a", 3.0, 7]]], ["c", 5.0, []]]

Note again that this is slightly different output than you specified, but I believe it's what you actually want. (What if more than one inner array matches per group?)

edited Apr 27, 2013 at 1:00

answered Apr 26, 2013 at 23:43

Darshan Rivka Whittle

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1 Comment

gkolan Over a year ago

I changed the output in the question to reflect what I actually meant as well! Now coming to the second question how to display lets say only the elements less than 8?

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