Merge and interleave two arrays in Ruby

Question

I have the following code:

a = [\"Cat\", \"Dog\", \"Mouse\"]
s = [\"and\", \"&\"]

I want to merge the array s into array <

Answer 1

Interleave 2D array of any size

arr = [["Cat", "Dog", "Mouse"],
 ["and", "&"],
 ["hello", "there", "you", "boo", "zoo"]]

max_count = arr.map(&:count).max
max_count.times.map{|i| arr.map{|a| a[i]}}.flatten.compact

#=> ["Cat", "and", "hello", "Dog", "&", "there", "Mouse", "you", "boo", "zoo"]

Answer 2

s.inject(a, :<<)

s   #=> ["and", "&"]
a   #=> ["Cat", "Dog", "Mouse", "and", "&"]

It doesn't give you the order you asked for, but it's a nice way of merging two arrays by appending to the one.

Answer 3

It's not exactly elegant, but it works for arrays of any size:

>> a.map.with_index { |x, i| [x, i == a.size - 2 ? s.last : s.first] }.flatten[0..-2] 
#=> ["Cat", "and", "Dog", "&", "Mouse"]

Answer 4

Here's a solution that allows interleaving multiple arrays of different sizes (general solution):

arr = [["Cat", "Dog", "Mouse", "boo", "zoo"],
 ["and", "&"],
 ["hello", "there", "you"]]

first, *rest = *arr; first.zip(*rest).flatten.compact
=> ["Cat", "and", "hello", "Dog", "&", "there", "Mouse", "you", "boo", "zoo"]

Answer 5

To handle the situation where both a & s are not of the same size:

a.zip(s).flatten.compact | s

• .compact will remove nil when a is larger than s
• | s will add the remaining items from s when a is smaller than s