ruby create sub arrays if element includes same letter -

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i have array this:

["b3", "a3", "a5", "b2"]

and need this:

[["b3", "b2"] ["a3", "a5"]]

i have tried various things including:

["b3", "a3", "a5", "b2"].map { |i| i.include? 'a' } # => returns [false, true, true, false] ["b3", "a3", "a5", "b2"].detect { |i| i.include? 'a' } # returns "a3"

is there simple way done?

thanks

a = ["b3", "a3", "a5", "b2"]  a.group_by { |s| s[0] }.values   #=> [["b3", "b2"], ["a3", "a5"]]

enumerable#group_by produces:

h = a.group_by { |s| s[0] }   #=> {"b"=>["b3", "b2"], "a"=>["a3", "a5"]}

and use hash#values extract values:

h.values   #=> [["b3", "b2"], ["a3", "a5"]]

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