Counting sort initialization of the output array, each take time. Therefore, the time for the whole algorithm is the sum of the times for these steps, . Because it uses arrays of length and , the total space usage of the algorithm is also . For problem instances in which the maximum key value is significantly smaller than the number of items, counting sort can be highly space-efficient, as the only storage it uses other than its input and output arrays is the Count array which uses space . If each item to be sorted is itself an integer, and used as
Radix sort via depth-first traversal, as in the above diagram, the number representations will always be on the leaf nodes of the trie. Note how similar in concept this particular example of a trie is to the recursive forward radix sort example which involves the use of buckets instead of a trie. Performing a radix sort with the buckets is like creating a trie and then discarding the non-leaf nodes. Radix sort In computer science, radix sort is a non-comparative integer sorting algorithm that sorts data with integer keys by grouping keys by the individual digits which share the same significant position