CODEWITHSUNDEEP
rubyhash
Ajay
Ajay

Reputation: 4251

How to have distinct key value pair from hash in ruby

I got a hash in following format:

{"A"=> 0, "B"=> 0, "C"=> 1, "D"=> 3, "E"=> 0}

And I want to have this hash with no duplicate value pairs. For instance, desired output is:

{ "A"=> 0, "C"=>1, "D"=>3 }

Upvotes: 1

Views: 351

Answers (2)

Shalev Shalit
Shalev Shalit

Reputation: 1963

  1. convert to Array, use uniq and convert back to Hash:

    Hash[some_hash.to_a.uniq(&:last)]

  2. invert keys and values and invert back:

    some_hash.invert.invert

  3. use set :

    require 'set'
set = Set.new
some_hash.select{ |_,v| !set.include?(v).tap{ set << v } }

Pay attention #1/#3 takes first elements while #2 takes the last ones

h = {a: 0, b: 1, c: 0, d: 2, e: 1}
Hash[h.to_a.uniq(&:last)] # {a: 0, b: 1, d: 2}
h.invert.invert           # {c: 0, d: 2, e: 1}

Benchmark ('a'..'zzz' hash)

        user     system      total        real
 #1   0.040000   0.010000   0.050000 (  0.040964)
 #2   0.010000   0.000000   0.010000 (  0.002194)
 #3   0.010000   0.000000   0.010000 (  0.010814)

Upvotes: 3

Andrey Deineko
Andrey Deineko

Reputation: 52357

You could do something like this:

h = {"A"=> 0, "B"=> 0, "C"=> 1, "D"=> 3, "E"=> 0}
arr = []
h.each {|k,v| arr.include?(v) ? h.delete(k) : arr << v }
#=> {"A"=>0, "C"=>1, "D"=>3}

Upvotes: 2

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