So, we actually don't know a lot about the "Viking" or Norse type of longship that would have been used in northern waters. I wrote about this before in a previous comment, which I can expand on:

[t]he "longship" has been romanticized in the stereotypical Viking community all out of proportion to its actual use, and also that our archaeological evidence of actual longships is highly fragmentary. (The Gokstad and Oseberg ships which exist in the popular imagination as the "longship" are of the same type and buried within a few years and a few miles of each other, and may not be typical of anything other than their own mid-9th century style).

All that said, what we think of as the modal Viking warship of the 8th-11th centuries was the longship, which that appears to be a (very small) replica of. The longship was classified by its number of "rooms" (defined as an area between thwarts, or cross-members) with an undecked longship presumably having as many thwarts/rooms as pairs of oars, which we also assume corresponds to pairs of warriors. These are large assumptions, but the records we have from ship-musters in Alfred's England (for example) talk about ships in terms of rooms, without a lot of evidence for manning.

In any case, a ship of less than 20 rooms wasn't considered much of a warship at all, with ships of 20-25 rooms seeming to be average. King Harald Hardrada had a 35-room ship built in 1061-62, which was extremely large. (The ships of 20-25 rooms were called esnecca, "snakes," while ships larger than say 30 rooms were called drekkar or "dragons," and seem to have been celebrated in sagas as very unusual.)

In general, though, ships used for exploring voyages were not of the longship type. Longships were distinct from trading vessels by being, well, long in proportion to their width. We have some evidence that the Norse used fatter (for lack of a better term) ships that were mostly propelled by sails and had oars only at the bow and stern; the Bayeux Tapestry depicts English forces using some of these types of ships, with shields hung over the gunwale and oars at the ends of the ship. These trading ships are more likely to be ones that made longer voyages, with longships and other ship types following once the navigation was well understood. The trading ships the Norse used (knarrar) would have been partially decked over, as would larger longships have been, and would have offered some shelter from the elements.

The defining feature of the longship seems to have been that it was, well, long -- "longship" is the word for it in English and the Scandinavian languages, and "snake" as I mentioned above is also a term for that type of warship.

The thing is, though, that we don't know how exactly they looked, and there were at least three different shipbuilding traditions at work in the North Sea. We know this because the Anglo-Saxon Chronicle says that "King Alfred had long ships built to oppose the [Danish] warships [lang scipu ongen ða aescas]. They were almost twice as long as the others. Some had 60 oars, some more. They were both swifter and steadier and also higher than the others. They were built neither on the Frisian nor the Danish pattern, but as it seemed to him himself that they could be useful." (Quoted in Rodger, Safeguard of the Seas pp. 15).

(As a sidenote: It's quite possible that "him himself" literally means that Alfred designed these himself; he was both a carpenter or at least familiar with carpentry and a seafarer.)

So the author(s) of the ASC were aware of at least three different shipbuilding traditions going on around England (the ships Alfred had built, the Frisian and the Danish ships). The Danish ships were probably warships, the Frisian ships were probably traders, and the English ships were built to counter the Danish ships. If they were in fact 30-room ships (with 60 oars) they would have been quite large for the time, with probably 2-3 times the crew of a 20-room ship.

In terms of being "advanced," that's a tricky question to get to. The Norse longships that we have (and again, remember that we have about a quarter of the Skuldelev 2 wreck, the Gosktad and Oseberg ships and that's pretty much it) were long, narrow, had good carrying capacity, and drew fairly little water, so they were ideal ships for the Norse type of raiding warfare that we know existed at the time. But they were not good for carrying large amounts of cargo (people built merchant ships for that) or apparently for defensive warfare (like Alfred's design was for). All ship design is a compromise, and "advanced" isn't really a useful comparison.

Does that answer your question?

The main source I'm drawing on for this other than Rodger, quoted above, is John Haywood's Dark Age Naval Power.