Question

我有一个Ruby数组，内容如下：

my_array
=> ["MPA5534285", "MPA5534555", "MPA553asdf5", "MPA553asdasdfasdfaf5"]

我有这样的Ruby哈希：

1.9.2p290 :012 > hash
 => {"MPA5534555"=>"something", "MPA553sf"=>"something", "MPA55345asdf5adfads"=>"something", "MPA553asdasdfasdfaf5"=>"something"}

我需要将数组与散列进行比较，并找到没有相应匹配的位置。

例如，在我的数组中，我有“MPA5534555”，如果我查看哈希，键确实存在。但是，在数组“MPA5534285”中没有哈希键。

我想要一个只有散列中没有键的数组。

Answer 1

a = ["MPA5534285", "MPA5534555", "MPA553asdf5", "MPA553asdasdfasdfaf5"]

h = {"MPA5534555"=>"something", "MPA553sf"=>"something", "MPA55345asdf5adfads"=>"something", "MPA553asdasdfasdfaf5"=>"something"} 


a - h.keys
# => ["MPA5534285", "MPA553asdf5"]

Answer 2

这个变体比a - h.keys稍快一点（无论如何都是在减去数组的情况下完成的，只是在这种情况下，h.keys的重组不是必需的）：

a.reject{ |e| h.has_key?(e) }

Answer 3

看到解决方案如何快速比较，总是很有趣：

require 'benchmark'

my_array = ["MPA5534285", "MPA5534555", "MPA553asdf5", "MPA553asdasdfasdfaf5"]
hash = {
  "MPA5534555"           => "something",
  "MPA553sf"             => "something",
  "MPA55345asdf5adfads"  => "something",
  "MPA553asdasdfasdfaf5" => "something"
}

n = 1_000_000

puts "For #{ n } loops:"
3.times do
  Benchmark.bm(8) do |b|
    b.report('keys')     { n.times { my_array - hash.keys                    } }
    b.report('has_key?') { n.times { my_array.reject{ |e| hash.has_key?(e) } } }
  end
end

运行时输出：

ruby ~/Desktop/test.rb 
For 1000000 loops:
              user     system      total        real
keys      3.910000   0.000000   3.910000 (  3.908089)
has_key?  2.590000   0.000000   2.590000 (  2.590154)
              user     system      total        real
keys      3.930000   0.010000   3.940000 (  3.934498)
has_key?  2.580000   0.000000   2.580000 (  2.583171)
              user     system      total        real
keys      3.940000   0.000000   3.940000 (  3.936036)
has_key?  2.590000   0.000000   2.590000 (  2.589483)

如何比较Ruby数组和哈希的内容？

3 个答案: