Introduction:

I saw there was only one other badminton related challenge right now. Since I play badminton myself (for the past 13 years now), I figured I'd add some badminton-related challenges. Here the first one:

Challenge:

Input: Two integers
Output: One of three distinct and unique outputs of your own choice. One indicating that the input is a valid badminton score AND the set has ended with a winner; one indicating that the input is a valid badminton score AND the set is still in play; one indicating the input is not a valid badminton score.

With badminton, both (pairs of) players start with 0 points, and you stop when one of the two (pairs of) players has reached a score of 21, with at least 2 points difference, up to a maximum of 30-29.

So these are all possible input-pairs (in either order) indicating it's a valid badminton score AND the set has ended:

[[0,21],[1,21],[2,21],[3,21],[4,21],[5,21],[6,21],[7,21],[8,21],[9,21],[10,21],[11,21],[12,21],[13,21],[14,21],[15,21],[16,21],[17,21],[18,21],[19,21],[20,22],[21,23],[22,24],[23,25],[24,26],[25,27],[26,28],[27,29],[28,30],[29,30]]

And these are all possible input-pairs (in either order) indicating it's a valid badminton score BUT the set is still in play:

[[0,0],[0,1],[0,2],[0,3],[0,4],[0,5],[0,6],[0,7],[0,8],[0,9],[0,10],[0,11],[0,12],[0,13],[0,14],[0,15],[0,16],[0,17],[0,18],[0,19],[0,20],[1,1],[1,2],[1,3],[1,4],[1,5],[1,6],[1,7],[1,8],[1,9],[1,10],[1,11],[1,12],[1,13],[1,14],[1,15],[1,16],[1,17],[1,18],[1,19],[1,20],[2,2],[2,3],[2,4],[2,5],[2,6],[2,7],[2,8],[2,9],[2,10],[2,11],[2,12],[2,13],[2,14],[2,15],[2,16],[2,17],[2,18],[2,19],[2,20],[3,3],[3,4],[3,5],[3,6],[3,7],[3,8],[3,9],[3,10],[3,11],[3,12],[3,13],[3,14],[3,15],[3,16],[3,17],[3,18],[3,19],[3,20],[4,4],[4,5],[4,6],[4,7],[4,8],[4,9],[4,10],[4,11],[4,12],[4,13],[4,14],[4,15],[4,16],[4,17],[4,18],[4,19],[4,20],[5,5],[5,6],[5,7],[5,8],[5,9],[5,10],[5,11],[5,12],[5,13],[5,14],[5,15],[5,16],[5,17],[5,18],[5,19],[5,20],[6,6],[6,7],[6,8],[6,9],[6,10],[6,11],[6,12],[6,13],[6,14],[6,15],[6,16],[6,17],[6,18],[6,19],[6,20],[7,7],[7,8],[7,9],[7,10],[7,11],[7,12],[7,13],[7,14],[7,15],[7,16],[7,17],[7,18],[7,19],[7,20],[8,8],[8,9],[8,10],[8,11],[8,12],[8,13],[8,14],[8,15],[8,16],[8,17],[8,18],[8,19],[8,20],[9,9],[9,10],[9,11],[9,12],[9,13],[9,14],[9,15],[9,16],[9,17],[9,18],[9,19],[9,20],[10,10],[10,11],[10,12],[10,13],[10,14],[10,15],[10,16],[10,17],[10,18],[10,19],[10,20],[11,11],[11,12],[11,13],[11,14],[11,15],[11,16],[11,17],[11,18],[11,19],[11,20],[12,12],[12,13],[12,14],[12,15],[12,16],[12,17],[12,18],[12,19],[12,20],[13,13],[13,14],[13,15],[13,16],[13,17],[13,18],[13,19],[13,20],[14,14],[14,15],[14,16],[14,17],[14,18],[14,19],[14,20],[15,15],[15,16],[15,17],[15,18],[15,19],[15,20],[16,16],[16,17],[16,18],[16,19],[16,20],[17,17],[17,18],[17,19],[17,20],[18,18],[18,19],[18,20],[19,19],[19,20],[20,20],[20,21],[21,21],[21,22],[22,22],[22,23],[23,23],[23,24],[24,24],[24,25],[25,25],[25,26],[26,26],[26,27],[27,27],[27,28],[28,28],[28,29],[29,29]]

Any other pair of integer would be an invalid badminton score.

Challenge rules:

• I/O is flexible, so:
  
  
  
  
  • You can take the input as a list of two numbers; two separated numbers through STDIN or function parameters; two strings; etc.
  
  
  • Output will be three distinct and unique values of your own choice. Can be integers (i.e. [0,1,2], [1,2,3], [-1,0,1], etc.); can be Booleans (i.e. [true,false,undefined/null/empty]); can be characters/strings (i.e. ["valid & ended","valid","invalid"]); etc.
  
  
  • Please specify the I/O you've used in your answer!
  
  
  
  


• You are allowed to take the input-integers pre-ordered from lowest to highest or vice-versa.


• The input integers can be negative, in which case they are of course invalid.

General rules:

• This is code-golf, so shortest answer in bytes wins.
  
  Don't let code-golf languages discourage you from posting answers with non-codegolfing languages. Try to come up with an as short as possible answer for 'any' programming language.


• 
  Standard rules apply for your answer with default I/O rules, so you are allowed to use STDIN/STDOUT, functions/method with the proper parameters and return-type, full programs. Your call.


• 
  Default Loopholes are forbidden.


• If possible, please add a link with a test for your code (i.e. TIO).


• Also, adding an explanation for your answer is highly recommended.

Test cases:

These test cases are valid, and the set has ended:

0 21

12 21

21 23

28 30

29 30

These test cases are valid, but the set is still in play:

0 0

0 20

12 12

21 21

21 22

These test cases are invalid:

-21 19

-19 21

-1 1

12 22

29 31

30 30

42 43

1021 1021

Jelly, 25 bytes

»19«28‘<‘×+2>ɗʋ⁹×,%Ƒ“œþ‘ɗ

Try it online!

Left argument: minimum. Right argument: maximum.

Invalid: 0. Ongoing: 1. Ended: 2.

C# (Visual C# Interactive Compiler), 53 52 bytes

a=>b=>b<0|a-b>2&a>21|b>29|a>30?3:a>20&a-b>1|a>29?1:2

Called as f(max)(min). Returns 3 for invalid, 1 for finished, 2 for ongoing.

Saved 1 byte thanks to Kevin Cruijjsen

Try it online!

Python 2, 97 95 75 72 71 70 bytes

lambda a,b:(-1<a<=b<22or 0<a>=b-2<b<31>a+1)and(20<b-(b<30)>a)+(a<20<b)

Try it online!

Takes input as pre-ordered a,b.

Returns 1, 0, False for ended, in play, invalid.

_{-1 byte, thanks to Kevin Cruijssen}

JavaScript (ES6),  55 53  48 bytes

^{Thanks to @KevinCruijssen for noticing that I was not fully assuming $ale b$ (saving 5 bytes)}

Takes input as (a)(b) with $ale b$. Returns $0$ (valid), $1$ (ended) or $2$ (invalid).

a=>b=>a<0|a>29|b>30|b>21&b-a>2?2:b>20&b-a>1|b>29

Try it online!

VDM-SL, 80 bytes

f(i,j)==if(j-i>2and j>21)or(i<0or i=30or j>30)then{}else{(j>20and j-i>1or j=30)} 

This function takes the scores ordered in ascending order and returns the empty set if the score is invalid or the set containing whether the set is complete (so {true} if the set is complete and valid and {false} if the set is incomplete and valid)

A full program to run might look like this:

functions

f:int*int+>set of bool

f(i,j)==if(j-i>2and j>21)or(i<0or i=30or j>30)then{}else{(j>20and j-i>1or j=30)}

Explanation:

if(j-i>2 and j>21)             /*if scores are too far apart*/

or(i<0 or i=30 or j>30)        /*or scores not in a valid range*/

then {}                        /*return the empty set*/

else{                       }  /*else return the set containing...*/

     (j>20 and j-i>1 or j=30)  /*if the set is complete*/