what flights are code shared?
 

what AS flights are code shared with other airlines?

Any AS flight number outside of 1-1xxx and 9xxx are codeshare flights. 2xxx flights are QX flights for AS. 3xxx are OO flights for AS. Since those are CAP flights there is an arguement that they are not codeshares. Any other AS flight number is more that likely a codeshare flight on partner metal.

Do you mean which AS-operated flights (or Horizon/Skywest flights operated on behalf of Alaska) have another airline's code on them? I think it's virtually all have at least one codeshare partner, but it's difficult or impossible to get a comprehensive list. Or do you mean which AS-marketed flights are operated by another airline? In that case, see [MENTION=401628]SNAnghbr[/MENTION]'s answer.

From the Alaska Website:

1–1999 operated by Alaska Airlines
2000–2999 operated by Horizon Air
3300–3499 operated by Skywest
4000–4799, 6000–6999, 8001–8199 operated by American Airlines
5000–5249 operated by Qantas
5500–5549 operated by Air Tahiti Nui
5550–5649 operated by Icelandair
5700–5999 operated by Qatar Airways
7310–7609 operated by Japan Airlines
7610–7709 operated by Finnair
7710–7999 operated by Iberia
8801–9000 operated by Condor

quick?
 

is there a quick way to find these departure/arriving cities?

7310–7609 operated by Japan Airlines

You can get a start with ExpertFlyer. Do a timetable search for all flights departing TYO (which covers HND and NRT), then filter and select only AS flights. I see ten out of HND, to BKK (2x), SIN (2x), SGN, HKG, LAX (3x), and SFO, plus ten more out of NRT. I have no idea how comprehensive that is. I would assume each flight has a counterpart in the opposite direction.

(It is much easier to search for what you're asking for — AS-marketed, JL-operated flights — than to find all marketing airlines for a given AS-operated flight. But still hard to get a complete list.)