Find the odd int (see https://www.codewars.com/kata/54da5a58ea159efa38000836/solutions/ruby)

bench_it.rb

module BenchIt
  require 'benchmark'
  ITERATIONS = 100_000

  def self.run_benchmark_multi(methods, arg_arrays, iterations=ITERATIONS, verbose=false)
    methods.each do |method|
      puts "\n#{method} iterations:#{iterations}:\n"
      Benchmark.bm do |x|
        x.report do
          iterations.times do |i|
            arg_arrays.each do |args|
              puts "Sending #{method.to_s}(#{args.to_s})" if verbose && i == 0
              send(method, *args)
            end
          end
        end
      end
    end
  end

end

benchmark_results.txt

alt1 iterations:100000:
       user     system      total        real
   5.470899   0.000000   5.470899 (  5.471308)

alt2 iterations:100000:
       user     system      total        real
   2.774857   0.000000   2.774857 (  2.775203)

alt3 iterations:100000:
       user     system      total        real
   2.761941   0.000000   2.761941 (  2.762190)

solution.rb

require 'securerandom'
require_relative './bench_it'

def solution(array_of_ints)
  counts = {}
  array_of_ints.each do |i|
    counts[i] = counts.fetch(i, 0) + 1
  end
  counts.each_pair { |k,v| return k if v.odd? }
  nil
end

def alt1(seq)
  seq.reduce(:^)
end

def alt2(seq)
  seq.detect { |n| seq.count(n).odd? }
end

def alt3(seq)
  seq.find{|c| seq.count(c).odd? }
end

def random_int_ara(size, max)
  ara = []
  (1..size).each do
    ara << SecureRandom.rand(max)
  end
  ara
end

test_data = [[[7]], [[0]] , [[1,1,2]], [[0,1,0,1,0]], [[1,2,2,3,3,3,4,3,3,3,2,2,1]]]

def basic_test
  data.each do |ara|
    puts "ara:#{ara}  solution:#{solution(*ara)}"
    puts "ara:#{ara}  alt1:#{alt1(*ara)}"
  end
end

benchmark_data = [
  [random_int_ara(1000, 100)],
  [random_int_ara(1000, 100)],
  [random_int_ara(1000, 100)]
]

BenchIt.run_benchmark_multi(%i[alt1 alt2 alt3], benchmark_data, 100_000)

Interesting !