Magic the Gathering: Friends or Foes?

Question

In the card game Magic: the Gathering there are five different colours, which represent loose affiliations of cards, White (W), Blue (U), Black (B), Red (R) and Green (G). These are often arranged in a pentagon as follows:

  W
G   U
 R B

Both in the lore of MtG as well as in many card mechanics, adjacent colours in this pentagon are usually considered allies, and non-adjacent (sort of opposite) colours are considered enemies.

In this challenge, you'll be given two colours and should determine their relationship.

The Challenge

You're given any two distinct characters from the set BGRUW. You may take these as a two-character string, a string with a delimiter between the characters, two separate character values, two singleton strings, two integers representing their code points, or a list or set type containing two characters/strings/integers.

Your output should be one of two distinct and consistent values of your choice, one which indicates that the two colours are allies and one which indicates that they are enemies. One of those two values may be no output at all.

You may write a program or a function and use any of the our standard methods of receiving input and providing output.

You may use any programming language, but note that these loopholes are forbidden by default.

This is code-golf, so the shortest valid answer – measured in bytes – wins.

Test Cases

There are only 20 possible inputs, so I'll list them all.

Friends:

WU   UB   BR   RG   GW   UW   BU   RB   GR   WG

Foes:

WB   UR   BG   RW   GU   BW   RU   GB   WR   UG

Answer 1

///, 40 bytes

//i//R///G///W///U///B///i/1/WUBRGWGRBUW

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Since /// has no other way of taking input, you need to put your input after the first /. An example of checking WG:

/WG/i//R///G///W///U///B///i/1/WUBRGWGRBUW

Itflabtijtslwi, 52 bytes

GGjGGGGkGG/jk/i//R///G///W///U///B///i/1/WUBRGWGRBUW

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Outputs a 1 if they are allies, otherwise outputs nothing.

The funny part is that it is actually a shorter answer than some "real" languages have.

You may be thinking, "You're not allowed to code the input in the program!" But you are allowed to do so if the language has no other way of getting input, as said here: meta.codegolf.stackexchange.com/a/10553/64159.

Thanks to Ørjan Johansen for the help with the Itflabtijtslwi port and making the interpreter. Very much.

Answer 2

Python 2, 56 46 28 Bytes

print input()in"WUBRGWGRBUW"

Takes input as a string and returns True or False if it is in the string b. Try it here! Thanks to @Григорий Перельман for removing 10 bytes! Thanks @SparklePony for removing another 18 bytes!

Answer 3

Brain-Flak, 78 bytes

(([(({}[{}]))]<>)){({}())<>}([]()(([])[]([][][]({}{}({}))))){{}}{}({()<{{}}>})

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This improves on DJMcMayhem's answer by streamlining the comparisons. It also uses the negative absolute value directly instead of using extra instructions to reach the positive absolute value.

Answer 4

Batch, 62 bytes

@set s=WUBRGWGRBUW
@call set t=%%s:%1=%%
@if %s%==%t% echo 1

Outputs 1 for foes, nothing for friends.

Answer 5

PowerShell, 42 34 32 bytes

'WUBRGWGRBUW'.indexof($args)-ge0

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Input is as a single string (e.g., RG), that is stringified $args and used as the .indexof() parameter for the color string. If the substring is not found, -1 is returned, so testing whether the result is -greater-than-or-equal to 0 suffices for a truthy/falsey output.

Saved two more bytes thanks to Philipp Leiß.

Answer 6

S.I.L.O.S, 53 bytes

loadLine
a=get 256
b=get 257
a*b
a%103
a%2
printInt a

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Input as a commmand line argument Please do note that this uses the method from the most upvoted answer

Answer 7

PHP, 45 Bytes

I know if I use a mod solution from someone else, that I can do it much shorter.

the absolute difference mod 17 mod 5 is 1 or 2

<?=abs(ord($t=$argv[1])-ord($t[1]))%17%5+1&2;

golfed down by @Titus from 64 Bytes

<?=in_array((abs(ord(($t=$argv[1])[0])-ord($t[1]))%17)%5,[1,2]);

PHP, 72 Bytes

the absolute difference mod 17 foes contains a digit between 3 and 5

<?=preg_match("#^[^3-5]+$#",(abs(ord(($t=$argv[1])[0])-ord($t[1]))%17));

PHP, 88 Bytes

the absolute difference mod 17 friends have a digit sum of 2 or 7

<?=in_array(array_sum(str_split((abs(ord(($t=$argv[1])[0])-ord($t[1]))%17))),[2,7])?1:0;

PHP >= 7.1, 81 Bytes

$p=strpos($s=WUBRG,($i=$argv[1])[0]);echo$i[1]==$s[$p!=4?$p+1:0]|$i[1]==$s[$p-1];

http://sandbox.onlinephpfunctions.com/code/9136a36084ecb5b397466e839210b50a88d8fe98

Answer 8

Java 8, 17 16 14 bytes

This is simply a Java lambda version of the same arithmetic solution everyone else is using. Takes two integral/character arguments containing the color codes as ASCII. Returns true if they are friends, false if foes.

Golfed:

a->b->a*b%51<9

Ungolfed:

import java.util.function.*;

public class MagicTheGatheringFriendsOrFoes {

  private static final char[][] FRIENDS = new char[][] { { 'W', 'U' }, { 'U', 'B' }, { 'B', 'R' }, { 'R', 'G' },
      { 'G', 'W' }, { 'U', 'W' }, { 'B', 'U' }, { 'R', 'B' }, { 'G', 'R' }, { 'W', 'G' } };

  private static final char[][] FOES = new char[][] { { 'W', 'B' }, { 'U', 'R' }, { 'B', 'G' }, { 'R', 'W' },
      { 'G', 'U' }, { 'B', 'W' }, { 'R', 'U' }, { 'G', 'B' }, { 'W', 'R' }, { 'U', 'G' } };

  public static void main(String[] args) {
    System.out.println("Friends: expect true");
    for (char[] friends : FRIENDS) {
      boolean result = f().apply(Integer.valueOf(friends[0])).apply(Integer.valueOf(friends[1]));
      System.out.println("(" + friends[0] + "," + friends[1] + ") = " + result);
    }

    System.out.println();
    System.out.println("Foes: expect false");
    for (char[] foes : FOES) {
      boolean result = f().apply(Integer.valueOf(foes[0])).apply(Integer.valueOf(foes[1]));
      System.out.println("(" + foes[0] + "," + foes[1] + ") = " + result);
    }
  }

  private static Function<Integer, IntFunction<Boolean>> f() {
    return a -> b -> a * b % 51 < 9;
  }
}

Answer 9

bash, 23 bytes

[[ WUBRGWGRBUW =~ $1 ]]

Exits/returns 0 (success/true) if friends, 1 (failure/false) if enemies.

This works by using the input string (for example, WU) as a regular expression using bash's builtin [[, which tests various things, in this case, the =~ operator of [[ is used to see if the first string WUBRGWGRBUW matches the regex (input string). Since the regex is not anchored by default, so long as the input string occurs anywhere in the "checked" string, [[ returns the status code 0, meaning the test result was true. If the input character pair did not occur anywhere in the string, it returns status code 1, meaning the test result was false. The tested string is a concatenation of all possible adjacent friend characters, so it's matched only by the friend-pair inputs.

Test:

for pair in WU UB BR RG GW UW BU RB GR WG WB UR BG RW GU BW RU GB WR UG
do
  bash -c '[[ WUBRGWGRBUW =~ $1 ]]' - $pair
  echo $pair $?
done

Answer 10

OIL, 77 bytes

Third-worst answer, but hey, it's OIL. Commented for clarity (remove spaces and C++-style comments for execution)

WU //storage, this just nops
UB
BR
RG
GW
UW
BU
RB
GR
WG
5  // read user input into line 10 (overwriting this line)
10
10 // test if what's in line 10 (the user input) &
10
0  // is identical to what's in line 0 (the first string) *
26 // if so, jump to line 26 (marked with %)
17 // else, jump to the next line
8  // increment line 14 (marked with *)
14
10 // test if line 14 is identical to
14
11 // what's in line 11 (a "10")
27 // if so, we checked all strings; so jump to line 27 (marked with $)
24 // else jump to the next line
6  // jump to line 12 (marked with &)
12
4  // print what's in line 4 ("GW" ≙ friend) %
4  // print what's in line 0 ("WU" ≙ foe) $

Prints GW if the colours are allies, WU otherwise (and if any unexpected input occurs).

Answer 11

Brain-Flak, 90 bytes

(<({}[{}])>)([[]()]((([])[][][])[][])){([({}<>)])<>}{}<>({<({}<>({}))>(){[()](<{}>)}{}<>})

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This beats the previous Brain-Flak answer by swapping getting the absolute value of the difference with creating negative copies of the differences to check. It also has slightly better number generation and difference checking

Answer 12

Whitespace, 60 bytes

[S S S N
_Push_0][S N
S _Duplicate_0][T   N
T   S _Read_input_as_character][T   T   T   _Retrieve_first_input][S N
S _Duplicate_first_input][S N
S _Duplicate_first_input][T N
T   S _Read_input_as_character][T   T   T   _Retrieve_second_input][T   S S N
_Multiply][S S S T  T   S S T   T   T   N
_Push_103][T    S T T   _Modulo][S S S T    S N
_Push_2][T  S T T   _Modulo][T  N
S T _Print_as_integer]

Letters S (space), T (tab), and N (new-line) added as highlighting only.
[..._some_action] added as explanation only.

Port of @Arnauld's 15-bytes JavaScript answer, so also outputs 0 for friends and 1 for foes.

Try it online (with raw spaces, tabs, and new-lines only).

Explanation in pseudo-code:

Integer a = read STDIN as character
Integer b = read STDIN as character
Integer t = a * b
t = t % 103
t = t % 2
Print t as integer to STDOUT

Answer 13

Pyth, 16 bytes

gx+J"WUBRGW"_JzZ

Test suite available online.

Explanation

gx+J"WUBRGW"_JzZ
   J"WUBRGW"      store string in variable J
  +         _J    concat J and reversed J
 x            z   get index of input in this string
g              Z  return if index >= 0 (will be -1 if not found)

Answer 14

JavaScript (ES6), 20 bytes

a=>b=>(a-b)%9%5%3!=0

let F = a=>b=>(a-b)%9%5%3!=0
let ch = [87, 85, 66, 82, 71];

console.log('Friends:');
console.log('WU/UW', F(ch[0])(ch[1]), F(ch[1])(ch[0]));
console.log('UB/BU', F(ch[1])(ch[2]), F(ch[2])(ch[1]));
console.log('BR/RB', F(ch[2])(ch[3]), F(ch[3])(ch[2]));
console.log('RG/GR', F(ch[3])(ch[4]), F(ch[4])(ch[3]));
console.log('GW/WG', F(ch[4])(ch[0]), F(ch[0])(ch[4]));

console.log('Foes:');
console.log('WB/BW', F(ch[0])(ch[2]), F(ch[2])(ch[0]));
console.log('UR/RU', F(ch[1])(ch[3]), F(ch[3])(ch[1]));
console.log('BG/GB', F(ch[2])(ch[4]), F(ch[4])(ch[2]));
console.log('RW/WR', F(ch[3])(ch[0]), F(ch[0])(ch[3]));
console.log('GU/UG', F(ch[4])(ch[1]), F(ch[1])(ch[4]));

Takes input as ascii character codes, passed in as F(a)(b) (one character each). Returns true for friends, false for foes.

Thanks to Mistah Figgins for the modulo idea.

Answer 15

QBIC, 29 bytes

;?instr(@WUBRG`+@W`+_fB|,A)>0

Explanation:

;       Gets the color combination as one strintg, "UG"
?       Print --> will eventually yield -1 for allies and 0 otherwise
instr(  Get the index of one string in antother. 
@WUBRG` The string to be searced is all allies, (@...` creates a string called B$)
+@W`      and an extra 'W' that we don't want to flip (prevents 'WW')
+_fB|    and all allies flipped --> WUBRGWGRBUW
,A)    The string to look for: "UG"
>0     If A is found in B+G+fB, this is >0, and PRINT will show -1 (QBasic's TRUE value)
       It prints 0 in all other cases.

This would be two bytes shorter if we could say that any positive value is true, and 0 is false...

Answer 16

C#, 37 Bytes

(string s)=>"GWUBRGRBUWG".Contains(s)

Answer 17

Perl 5, 18 bytes

$_=WUBRGWGRBUW=~$_

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Takes input as a two letter string, upper case. Outputs 1 (true) for allies, nothing (false) for enemies.

Answer 18

Thunno 2, 7 bytes

×.6/4Æ&

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Link is to verify all test cases. Port of Arnauld's JS answer.

Explanation

×.6/4Æ&  # Implicit input as charcodes
×        # Multiply the two charcodes together
 .6/     # Divide this result by 0.6
    4Æ&  # Bitwise AND with 4
         # Implicit output