What is the most efficient way to sort hashes in ruby?

Question

I am trying to sort about 20 hashes in ruby based on one of the attributes of the array. I want to only return the top 3 hash keys , but I don't want to have to compare each one.

Here is an example below of something similar to what I am trying to sort. I want to sort based on powerrank.

["green", {:price=>24.88, :numreviews=>822, :avgStarsRank=>41.0, :reviewsrank=>28, :powerrank=>73.976}]

["steve", {:price=>14.96, :numreviews=>3, :avgStarsRank=>40.0, :reviewsrank=>0, :powerrank=>42.992000000000004}]

["joey", {:price=>40.27, :numreviews=>814, :avgStarsRank=>44.0, :reviewsrank=>28, :powerrank=>80.054}]

["board", {:price=>14.96, :numreviews=>3, :avgStarsRank=>40.0, :reviewsrank=>0, :powerrank=>47}]

["john", {:price=>40.27, :numreviews=>814, :avgStarsRank=>44.0, :reviewsrank=>28, :powerrank=>16}]

For this, all I would want back would an array with ["joey", "green", "board"]. Any suggestions on how to tackle this issue?

Edit: Here is the example in the original hash form:

powerrankings =
    {
        "green"=>{:price=>24.88, :numreviews=>822, :avgStarsRank=>41.0, :reviewsrank=>28, :powerrank=>73.976}, 
        "steve"=>{:price=>14.96, :numreviews=>3, :avgStarsRank=>40.0, :reviewsrank=>0, :powerrank=>42.992000000000004}, 
        "joey"=>{:price=>40.27, :numreviews=>814, :avgStarsRank=>44.0, :reviewsrank=>28, :powerrank=>80.054}}
        "board"=>{:price=>14.96, :numreviews=>3, :avgStarsRank=>40.0, :reviewsrank=>0, :powerrank=>47}, 
        "john"=>{:price=>40.27, :numreviews=>814, :avgStarsRank=>44.0, :reviewsrank=>28, :powerrank=>16}
    }

Answer 1

Assuming that powerrankings is not as you showed but is rather,

powerrankings = {
  "green" => {:price=>24.88, :numreviews=>822, :avgStarsRank=>41.0, :reviewsrank=>28, :powerrank=>73.976}, 
  "steve" => {:price=>14.96, :numreviews=>3, :avgStarsRank=>40.0, :reviewsrank=>0, :powerrank=>42.992000000000004}, 
  "joey" => {:price=>40.27, :numreviews=>814, :avgStarsRank=>44.0, :reviewsrank=>28, :powerrank=>80.054},
  "board" => {:price=>14.96, :numreviews=>3, :avgStarsRank=>40.0, :reviewsrank=>0, :powerrank=>47}, 
  "john" => {:price=>40.27, :numreviews=>814, :avgStarsRank=>44.0, :reviewsrank=>28, :powerrank=>16}
}

then,

powerrankings.sort_by{|_, h| h[:powerrank]}.reverse.first(3).map(&:first)
# => ["joey", "green", "board"]