The topic of the efficiency of radix sort compared to other sorting algorithms is somewhat tricky and subject to quite a lot of misunderstandings. Whether radix sort is equally efficient, less efficient or more efficient than the best comparison-based algorithms depends on the details of the assumptions made. Radix sort efficiency is O(d·n) for n keys which have d or fewer digits. Sometimes d is presented as a constant, which would make radix sort better (for sufficiently large n) than the best comparison-based sorting algorithms, which are all O(n·log(n)) number of comparisons needed. However, in general d cannot be considered a constant. In particular, under the common (but sometimes implicit) assumption that all keys are distinct, then d must be at least of the order of log(n), which gives at best (with densely packed keys) a time complexity O(n·log(n)). That would seem to make radix sort at most equally efficient as the best comparison-based sorts (and worse if keys are much longer than log(n)).