How can I delete duplicate values from a hash of hash

Question

I need a unique hash , where the value of "one" should never repeat.

for example,

hash= {"1"=>{"one"=>1,"two"=>2},
   "2"=>{"one"=>1,"two"=>3},
   "3"=>{"one"=>2,"two"=>3},
   "4"=>{"one"=>1,"two"=>2}}

then the result should be,

hash= {"1"=>{"one"=>1,"two"=>2},
    "3"=>{"one"=>2,"two"=>3}}

David Unric · Accepted Answer · 2015-06-03 12:23:02Z

5

(readable) one-liner:

hash.to_a.uniq {|(_,v)| v['one']}.to_h
# {"1"=>{"one"=>1, "two"=>2}, "3"=>{"one"=>2, "two"=>3}}

answered Jun 3, 2015 at 12:23

David Unric

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Comments

BinaryMee · Accepted Answer · 2015-06-03 09:29:13Z

2

ones_values = {}
hash.delete_if do |key, value|
  ones_values[value["one"]] ? true : (ones_values[value["one"]] = true) && false
end

edited Jun 3, 2015 at 9:29

answered Jun 3, 2015 at 9:07

BinaryMee

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Comments

Aleksei Matiushkin · Accepted Answer · 2015-06-03 09:02:38Z

2

hash.inject({}) do |memo, (k, v)| 
  memo[k] = v unless memo.values.any? do |mv| 
                       mv['one'] == v['one']
                     end
  memo
end

#⇒ {
#    "1" => {
#      "one" => 1,
#      "two" => 2
#    },
#    "3" => {
#      "one" => 2,
#      "two" => 3
#    }
#  }

answered Jun 3, 2015 at 9:02

Aleksei Matiushkin

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2 Comments

jissy Over a year ago

for the above set of values the answer is ok .But , when i implemented it in rails for some hash i got the following message: undefined method `values' for nil:NilClass

Aleksei Matiushkin Over a year ago

The code above can’t produce this error message. You introduce some error while implementing it in rails. It looks like you’ve forgotten to return memo from each loop iteration.

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