Created
May 2, 2014 00:29
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How can I extract the bigger value for each key in a list of hashes in Ruby
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Many concepts here to revisit, so saving in gist. | |
http://stackoverflow.com/questions/21712814/how-can-i-extract-the-bigger-value-for-each-key-in-a-list-of-hashes-in-ruby/21729254?noredirect=1#comment32860522_21729254 | |
a = [{1=>19.4}, {1=>12.4}, {2=>29.4}, {3=>12.4}, {2=>39.4}, {2=>59.4}] | |
# the below is the main trick, to group the hashes and sorted the key/value pair | |
# in **ascending order**. | |
a.sort_by(&:to_a) | |
# => [{1=>12.4}, {1=>19.4}, {2=>29.4}, {2=>39.4}, {2=>59.4}, {3=>12.4}] | |
# then using the trick in mind, we know hash can't have duplicate keys, so | |
# blindly I can rely on `Enumerable#inject` with the `Hash#merge` method. | |
a.sort_by(&:to_a).inject(:merge) | |
# => {1=>19.4, 2=>59.4, 3=>12.4} | |
# final one | |
a.sort_by(&:to_a).inject(:merge).map { |k,v| {k => v} } | |
# => [{1=>19.4}, {2=>59.4}, {3=>12.4}] |
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