Benchmarks when removing duplicate items from array

gistfile1.rb

require 'benchmark'

arr1 = (1..5000).to_a
arr2 = (1..10000).to_a

a = arr1.zip(arr2).flatten # 10000 items, 5000 duplicates

# with #uniq
puts Benchmark.measure { a.uniq }
#                                   Total time
# => 0.000000   0.000000   0.000000 (  0.001759)


# with #each
puts Benchmark.measure {
  counts = Hash.new(0)
  a.each { |v| counts[v] += 1 }
  counts.select { |v, count| count == 1 }.keys
}
#                                   Total time
# => 0.000000   0.000000   0.000000 (  0.003177)

# with inject:
puts Benchmark.measure { a.inject([]) { |arr, i| arr << i unless arr.include? i; arr } }
#                                   Total time
# => 0.920000   0.000000   0.920000 (  0.923349)