removing duplicates in array of arrays in Ruby -

i have array of arrays, this:

aa = [ [a,d], [a,d1], [a,d], [b,d], [b,d2], [b,d3], [b,d2], [a,d2] ] 

i have unique array of arrays, not on first element - can doing aa.uniq(&:first) - rather remove inner arrays if both values match. result be:

aa = [ [a,d], [a,d1], [a,d2], [b,d], [b,d2], [b,d3] ] 

can assist in pointing me efficient way of doing this? have large nr of arrays - in order of 1 million - need process.

any appreciated! john

if need maintain collection of elements where each element unique , order not important. should use set. instance,

require 'set' my_set = set.new my_set << [1, 'a'] my_set << [1, 'a'] my_set << [1, 'b'] my_set.each { |elem| puts "#{elem}" } 

it give you

[1, "a"] [1, "b"] 

if order important, use uniq! on array

aa.uniq!