eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2014-09-04
654
668
10.4230/LIPIcs.APPROX-RANDOM.2014.654
article
Unidirectional Input/Output Streaming Complexity of Reversal and Sorting
François, Nathanaël
Jain, Rahul
Magniez, Frédéric
We consider unidirectional data streams with restricted access, such as read-only and write-only streams. For read-write streams, we also
introduce a new complexity measure called expansion, the ratio between
the space used on the stream and the input size. We give tight bounds for the complexity of reversing a stream of length n in several of the possible models. In the read-only and write-only model, we show that p-pass algorithms need memory space Theta(n/p). But if either the output stream or the input stream is read-write, then the complexity falls to Theta(n/p^2). It becomes polylog(n) if p = O(log n) and both streams are read-write. We also study the complexity of sorting a stream and give two algorithms with small expansion. Our main sorting algorithm is randomized and has O(1) expansion, O(log n) passes and O(log n) memory.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol028-approx-random2014/LIPIcs.APPROX-RANDOM.2014.654/LIPIcs.APPROX-RANDOM.2014.654.pdf
Streaming Algorithms
Multiple Streams
Reversal
Sorting