creating an array with information contained in two other arrays

Question

how can I buit an array using two arrays as follow:

name = [a, b, c]

how_many_of_each [3, 5, 2]

to get

my_array = [a, a, a, b, b, b, b, b, c, c]

Answer 1

Use zip, flat_map, and array multiplication:

irb(main):001:0> value = [:a, :b, :c]
=> [:a, :b, :c]
irb(main):002:0> times = [3, 5, 2]
=> [3, 5, 2]
irb(main):003:0> value.zip(times).flat_map { |v, t| [v] * t }
=> [:a, :a, :a, :b, :b, :b, :b, :b, :c, :c]

Answer 2

name.zip(how_many_of_each).inject([]) do |memo, (x, y)|
  y.times { memo << x}
  memo
end

=> [:a, :a, :a, :b, :b, :b, :b, :b, :c, :c]

EDIT: Oh well, there's better, see @David Grayson.

Answer 3

This will do it in an easy to understand way:

my_array = []
name.count.times do |i|
    how_many_of_each[i].times { my_array << name[i] }
end