Generate all combinations of given list of elements, sorted

Jelly, 1 byte

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Cartesian power built-in atom, as a dyadic link with left argument the items and right argument the count, or as a full program with first argument the items and second argument the count.

Haskell, 20 bytes

(mapM id.).replicate

Usage exaple:

*Main> ( (mapM id.).replicate )  2 "01" 
["00","01","10","11"]
*Main> ( (mapM id.).replicate )  2 "10" 
["11","10","01","00"]

replicate makes n copies of the 2nd parameter and mapM id builds the combinations. Btw, mapM id is the same as sequence, but 1 byte less.

MATL, 2 bytes

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Cartesian power builtin...

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