Ruby - putting array elements into another array in order

Question

array1 = [ [a], [b], [c], [d], [e] ]

array2 = [1, 2, 3, 4, 5, ...]

How can I put each of the elements of array2 into each the elements of array1 to get something like:

array3 = [ [a, 1], [b, 2], [c, 3], [d, 4], ... ]

I'm trying something like array1.map { |a| [a, array2.each { |b| b}] }, but not really sure how to get it yet.

Thanks!

Is the value in array2 an index into array1, or do you want to combine the arrays according to their position in each array? — Kevin Keane
– Kevin Keane, Commented Apr 20, 2015 at 21:31

Nafaa Boutefer · Accepted Answer · 2015-04-20 22:09:30Z

8

Just try this using Array#flatten and Array#zip

array1 = [ ['a'], ['b'], ['c'], ['d'], ['e'] ]
array2 = [1, 2, 3, 4, 5]
array1.flatten.zip(array2) 
# [["a", 1], ["b", 2], ["c", 3], ["d", 4], ["e", 5]]

More information about Array#zip can be found here.

edited Apr 20, 2015 at 22:09

anon

answered Apr 20, 2015 at 21:33

Nafaa Boutefer

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2 Comments

Sid Over a year ago

@QPaysTaxes This blog post (not mine) has a great explanation of ruby zip method.

anon Over a year ago

@Sid So put it in your answer so that people (like me cough) who aren't familiar with .zip can see it right in the an-- oh, you already did. Uh. Good! Good on you. I'm gonna, uh... Be over here.

Cary Swoveland · Accepted Answer · 2015-04-20 22:21:46Z

array1 = [ ['a'], ['b'], ['c'], ['d','e'] ]
array2 = [1, 2, 3, 4]

If you do not wish to alter array1 or array2:

array1.zip(array2).map { |a1,e2| a1 + [e2] }
  #=> [["a", 1], ["b", 2], ["c", 3], ["d", "e", 4]]
array1
  #=> [ ['a'], ['b'], ['c'], ['d','e'] ]

If you do wish to alter array1 but not array2:

array1.zip(array2).map { |a1,e2| a1 << e2 }
  #=> [["a", 1], ["b", 2], ["c", 3], ["d", "e", 4]]
array1
  #=> [["a", 1], ["b", 2], ["c", 3], ["d", "e", 4]]

If you do wish to alter array1 and can also alter array2:

array1.map { |a| a << array2.shift }
  #=> [["a", 1], ["b", 2], ["c", 3], ["d", "e", 4]] 
array1
  #=> [["a", 1], ["b", 2], ["c", 3], ["d", "e", 4]] 
array2
  #=> []

In the first two cases you could use Array#transpose instead of Array#zip by replacing array1.zip(array2) with [array1, array2].transpose.

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