Combinations with Repetitions

This problem is similar to Enumerating Combinations, however there is minor but significant difference.

We again are interested in building combinations of K elements of the given set of size N. However, some elements within the set could be duplicated. Let's call it Combinations with limited repetitions. For example think of the set:

0 1 1 2 3

If we try to build combinations of 3 elements, we'll found that instead of 10 only the following 7 will do:

011 012 013 023 112 113 123

Input data contain the value K and the set of elements (digits from 0 to 9) in form "K of X Y ... Z".
Answer should contain all possible combinations in lexicographic order.

Example:

input data:
3 of 0 1 1 2 3 3 3 4

answer:
011 012 013 014 023 024 033 034 112 113 114 123 124 133 134 233 234 333 334

Note: you may expect that there would be from 200 to 1000 results.