Ruby: How to remove specific digits from integers that are inside an array?

Question

I'm new to programming. I would like to take an array of Integers, like [155, 151, 2, 15] and remove a specific digit, in this case 5, and add up the new numbers. I've broken this problem up into smaller steps, and gotten the result I wanted. I'm just wondering if there are easier ways to do a problem like this? Maybe a different method I could use? Any help is greatly appreciated.

Here is the code I have:

 arr = [155, 151, 2, 15]
# goal: remove the 5 digit from values and add 
#       new numbers together --> 1 + 11 + 2 + 1 == 15

# convert to arr of strings and delete zeros
str_arr = []
arr.each do |el|
  str_arr << el.to_s.delete('5')
end

# convert to arr of nums
num_arr = []
str_arr.each do |el|
  num_arr << el.to_i
end

# reduce num_arr
num_arr.reduce(:+)

Answer 1

Maybe you can use map instead each, this way you avoid having to push to a new initialized array each element transformed inside the block, like:

p [155, 151, 2, 15].map { |el| el.to_s.delete('5').to_i }.reduce(:+)
# 15

If using ruby 2.4 or higher you can use Enumerable#sum instead reduce (which seems to be a faster option).

p [155, 151, 2, 15].sum { |el| el.to_s.delete('5').to_i }
# 15

Answer 2

arr = [155, 151, 2, 15]

arr.sum { |n| (n.digits - [5]).reverse.join.to_i }
  #=> 15

Answer 3

using eval :

eval(arr.join('+').delete('5'))    
#=> 15

using inject :

arr.inject(0){|sum, element| element.to_s.delete('5').to_i + sum } 
#=> 15

The solution using eval is more fun, but the solution using inject is arguably easier to understand. Cheers.