Editing Bucket sort (section)

===Postman's sort===<!-- This section is linked from [[Radix sort]] -->
The '''Postman's sort''' is a variant of bucket sort that takes advantage of a hierarchical structure of elements, typically described by a set of attributes. This is the algorithm used by letter-sorting machines in [[post office]]s: mail is sorted first between domestic and international; then by state, province or territory; then by destination post office; then by routes, etc. Since keys are not compared against each other, sorting time is O(''cn''), where ''c'' depends on the size of the key and number of buckets. This is similar to a [[radix sort]] that works "top down," or "most significant digit first."<ref>{{Cite web|url=http://www.rrsd.com/psort/cuj/cuj.htm|title = Robert Ramey Software Development}}</ref>