In response to https://www.ruby-forum.com/topic/4422661

arup_delete_three.rb

#!/usr/bin/env ruby
#coding: utf-8

def del_first_three_original_1(a)
  num_to_del = a.find { |e| a.count(e) >= 3 }
  return a if num_to_del.nil?
  3.times do
    ind = a.index { |e| e == num_to_del }
    a.delete_at(ind)
  end
  a
end

def del_first_three_original_2(a)
  num_to_del = a.find { |e| a.count(e) >= 3 }
  return a if num_to_del.nil?
  3.times do
    ind = a.index { |e| e == num_to_del }
    a.tap { |ob| ob.delete_at(ind) }
  end
end


def del_first_three_refactored(ary)
  el_indices = Hash.new { |hash, key| hash[key] = Array.new }
  ary.each_with_index do |el, ix|
    el_indices[el].push ix
    if el_indices[el].size >= 3
      el_indices[el].each_with_index do |del_ix, offset|
        ary.delete_at(del_ix - offset)
      end
      break ary
    end
  end
end

ary = Array.new

3.times { ary.push 0 }

(1..100_000_000).each { |n| ary.push n }

ary_original_1 = ary.dup
ary_original_2 = ary.dup
ary_refactored = ary.dup

t1 = Time.now
del_first_three_original_1(ary_original_1)
t2 = Time.now
puts "Original (1) lasted #{t2-t1} seconds"

t1 = Time.now
del_first_three_original_2(ary_original_2)
t2 = Time.now
puts "Original (2) lasted #{t2-t1} seconds"

t1 = Time.now
del_first_three_refactored(ary_refactored)
t2 = Time.now
puts "Refactored lasted #{t2-t1} seconds"

puts "Results are correct" if ary_original_1 == ary_original_2 and ary_original_2 == ary_refactored
puts RUBY_DESCRIPTION