Merge two values

Question

You have two values each of which is either 0 representing "unknown", or one of 1,2,3. Merge them into a single value as follows:

• If both values are nonzero and equal, output that value:
  (3,3) -> 3
• If both values are nonzero but unequal, output 0 for unknown:
  (1,2) -> 0
• If one value is zero and the other is not, output the nonzero value:
  (2,0) -> 2, (0,1) -> 1
• If both values are zero, output zero:
  (0,0) -> 0

Test cases:

There are 16 possible input pairs.

  | 0 1 2 3
--+--------
0 | 0 1 2 3
1 | 1 1 0 0
2 | 2 0 2 0
3 | 3 0 0 3

(0, 0) -> 0
(0, 1) -> 1
(0, 2) -> 2
(0, 3) -> 3
(1, 0) -> 1
(1, 1) -> 1
(1, 2) -> 0
(1, 3) -> 0
(2, 0) -> 2
(2, 1) -> 0
(2, 2) -> 2
(2, 3) -> 0
(3, 0) -> 3
(3, 1) -> 0
(3, 2) -> 0
(3, 3) -> 3

Leaderboards

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Answer 1

C#, 4827 bytes

(x,y)=>x==y?x:(x*y>0?0:x|y)

Try it online

Thanks @Charlie for the TIO link & helping trim 21 chars off the code

Answer 2

PHP, 42 40 bytes

[,$a,$b]=$argv;echo$a*$b&&$a-$b?0:$a|$b;

Run with php -r '<code>' <a> <b> or Try it online.

breakdown

[,$a,$b]=$argv; // import input
echo
    $a*$b       // if both not 0
    &&$a-$b     // and unequal
        ?0      // then print 0
        :$a|$b  // else print the non-zero value, if there is one
;

Answer 3

Husk, 4 bytes

-1 thanks to H.PWiz.

!4uΘ

Try it online!

Answer 4

Q'Nial7, 40 bytes

n is OP A B{2>sum(cull A B 0>0)*max A B}

n is OP A B{                           }    operation n with parameters A B (pair of numbers)
                       A B 0                append 0 to pair of numbers
                  cull                      create list of unique elements
                            >0              create booleans of elements that are > 0
              sum(            )             sum up the booleans
            2>                              sum > 2 ? (boolean)
                               *max A B     multiply boolean with max of A B

result:

     n 0 3
3
     n 1 2
0
     n 2 2
2
     n 0 0
0