Elegant solutions

Im bored, show me some good code (any language whatsoever)
Post a problem, then a great solution.

1) Transpose a matrix
(apply #'mapcar #'list '(( 1  2  3  4)
                         ( 5  6  7  8)
                         ( 9 10 11 12)
                         (13 14 15 16)))
(( 1  5  9 13)
 ( 2  6 10 14)
 ( 3  7 11 15)
 ( 4  8 12 16))

>>23
are you a troll, or just a dumbass? you were supposed to CODE the "set" function! the set function, in fact, it's all you were supposed to code.

there are many ways of writing "uniq", depending if you want efficience or not, or if you want to preserve the order, or not.