RadixSort

Radix Sort.

A non-comparative sorting algorithm that sorts integers by processing individual digits from least significant to most significant. Uses counting sort as a stable subroutine per digit. Achieves O(nk) time where k is the number of digits in the max value.

Note: this implementation handles non-negative integers only. For generic types, elements are sorted by their natural or comparator-defined rank, falling back to comparison-based counting.