问题
I've run into a peculiar problem which I don't seem to be able to wrap my head around. I'll get right into it.
The problem is matching a set of cards to a set of rules.
It is possible to define a set of rules as a string. It is composed of comma separated tuples of <suit>:<value>. For example H:4, S:1 should match Four of Hearts and Ace of Spades. It is also possible to wildcard, for example *:* matches any card, D:* matches any card with in the diamond suit, and *:2matches a Two in any suit. Rules can be combined with comma: *:*,*:*,H:4 would match a set of cards if it held 2 random cards and a Four of Hearts.
So far so good. A parser for this is easy and straight forward to write. Here comes the tricky part.
To make it easy to compose these rules, two more constructions can be used for suit and value. These are < (legal for suit and value) and +n (legal only for value) where n is a number. < means "the same as previous match" and +n means "n higher than previous match". An example:
*:*, <:*, *:<
Means: match any card, then match a card with the same suit as the first match, next match another card with the same value as the second match. This hand would match:
H:4,H:8,C:8
Because Hearts of Four and Hearts of Eight is the same suit, while Eight of Hearts and Eight of Clubs is the same value.
It is allowed to have more cards as long as all rules match (so, adding C:10 to the above hand would still match the rule).
My first approach at solving this is basically taking the set of cards which should be matched, attempting to apply the first rule to it. If it matched, I moved on to the next rule and attempted to match it from the set of cards, and so on until either all rules were matched, or I found a rule that didn't match. This approach have (at least) one flaw, consider example above above: *:*,<:*,*:<, but with the cards in this order: H:8,C:8,H:4.
- It would match the H:8 of for the first rule.
Matched: H:8 - Next it attempts to find one with the same suit (Hearts). There is a Four of Hearts.
Matched: H:8, H:4 - Moving on, it want to find a card with the same value (Four), and fails.
I don't want the way the set of cards is ordered to have any impact on the result as it does in the above example. I could sort the set of cards if I could think of any great strategy that worked well with any set of rules.
I have no knowledge of the quantity of cards or number oof rules, so a brute force approach is not feasible.
Thank you for reading this far, I am grateful for any tip or insight.
回答1:
Your problem is actually an ordering problem. Here's a simple version for it:
given an input sequence of numbers and a pattern, reorder them so that they fit the pattern. The pattern can contain "*", meaning "any number" and ">", meaning "bigger than the previous number.
For example, given pattern [* * > >] and sequence [10 10 2 1] such an ordering exists and it is [10 1 2 10]. Some inputs might give no outputs, others 1, while even others many (think the input [10 10 2 1] and the pattern [* * * *]).
I'd say that once you have the solution for this simplified problem, switching to your problem is just a matter of adding another dimension and some operators. Sorry for not being of more help :/ .
LE. keep in mind that if the allowed character symbols are finite (i.e. 4) and also the allowed numbers (i.e. 9) things might get easier.
来源：https://stackoverflow.com/questions/12061439/algorithm-for-matching-cards-to-a-set-of-rules