For the quick-sort case, log n need not be 64. That presumes no duplicates. In the problem to be solved. duplicates matter. Now, in practice it seems unlikely t

For the quick-sort case, log n need not be 64. That presumes no duplicates. In the problem to be solved. duplicates matter. Now, in practice it seems unlikely that more than 2^64 integers will need to be sorted, but for the rigor of asymptotic notation, you need to consider that case. I'd like to add that the tree-structure needed for radix sort is going to make it useless in practice. Trees are essentially synonymous with cache-misses.