Radix Sort

This sort was originally used to sort computer punch-card decks.

It is currently used for multi-key sorts (eg., year/month/day)

Consider each digit of the number as a separate key

Idea 1: Sort on most significant digit n, then sort on digit n-1, etc.

Problem: For old sorters, sort into 10 bins, but subsequent recursive sorts require all 10 bins. Operator must store the other 9 piles.

Idea 2: Sort on least significant digit, then sort on next least significant digit, etc.