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Challenges

Operation "Find The Operator"

+7
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Challenge

Make a program that takes input of 3 non-negative integers: a result and 2 other values that once calculated results to the 3rd value.

  • The program must figure out how to get the 2 first numbers to equivalence itself with the 3rd. It could be either addition, subtraction, multiplication, integer division, modulo and exponentiation.
  • You can't change the places of the 2 variables when building the equation, meaning you can't get some value by intertwining in the methods excluding addition and multiplication.
  • The returning value is the operator that makes the equation true (it's best to use some distinguishable character to separate it from the other methods).
  • Use whatever characters you want to use to determine the method that makes the equation truthy.
  • If multiple operators make the equation truthy, then output them in any order.
  • What makes it true? If an equation exists within the 2 numbers that results to the value of the 3rd.
  • What to return when it's false? Something but not nothing (whitespaces and newlines aren't allowed as such output).
  • This is code-golf so the shortest program wins!

Test Cases

# Input (#, #, #)
// Output (+-*/%^ or .)

2 3 5
+

7 3 2
/

9 8 4
.

1 2 2
*

2 2 4
+ * ^

14 6 8
-

5 0 2
.

0 0 1
^

8 4 0
%

0 0 0
+ - *
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5 answers

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+4
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C (gcc), 147 151 bytes

#define L(X)X(+,a+b)X(-,a-b)X(*,a*b)X(/,b&&a/b)X(%,b&&a%b)X(^,pow(a,b))
#define M(o,d)printf("%s",d==c?#o" ":z++==5?".":"");
z;s[99];f(a,b,c){L(M)}

Try it online!

Somewhat naive solution with X macros that builds up a string before printing. The b&&a/b checks are there to deal with division by zero.

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+3
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Python 3, 106 91 bytes

Saved 15 bytes thanks to Moshi in the comments

lambda a,b,c:[p for p in"+ - * // % **".split()if(p in'+-**'or b)and eval(f"{a}{p}{b}")==c]

Try it online!

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Further improvements (1 comment)
91 bytes with list comprehension (2 comments)
+2
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Ruby, 58 bytes

Simple eval solution. Using ** for exponentiation.

->a,b,c{%w[+ - * / % **].select{eval("#{a}#{_1}#{b}")==c}}

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+1
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Ruby, 57 bytes

->a,b,c{%w[+ - * / % **].select{c==a.send(_1,b)rescue p}}

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Japt, 16 bytes

Takes the result as the first input and the other 2 values as an array as the second input. Uses z for floor division & p for exponentiation and outputs " if there's no match (costing 3 bytes :\)

"+-*z%p"ƶVrXêQ

Try it

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I'm not sure the conditions allow reordering the input values that way. Maybe Mark Giraffe can clarif... (2 comments)

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