this post was submitted on 07 Dec 2023
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God I wish there was an easier way to do this (programming.dev)
submitted 2 years ago* (last edited 2 years ago) by andioop@programming.dev to c/programming_horror@programming.dev
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[–] olafurp@lemmy.world 1 points 2 years ago (1 children)

Of course there's an easier way. Just integrate the state of the art API dedicated for this exact problem. https://isevenapi.xyz/

[–] misophist@lemmy.world 1 points 2 years ago

This is confusing. I'm already using the iSeven API to determine if a number is 7. I'm getting a namespace collision error when I try to load this new API. Bug report filed.

[–] noddy@beehaw.org 1 points 2 years ago* (last edited 2 years ago) (1 children)

I know how to fix this!

bool IsEven(int number) {
    bool even = true;
    for (int i = 0; i < number; ++i) {
        if (even == true) {
            even = false;
        }
        else if (even == false) {
            even = true;
        }
        else {
            throw RuntimeException("Could not determine whether even is true or false.");
        }
    }

    if (even == true) {
        return even ? true : false;
    }
    else if (even == false) {
        return (!even) ? false : true;
    }
    else {
        throw RuntimeException("Could not determine whether even is true or false.");
    }
}
[–] odium@programming.dev 0 points 2 years ago (1 children)

Have you tried seeing if the recursive approach runs faster?

[–] noddy@beehaw.org 1 points 2 years ago

I know an even better way. We can make it run in O(1) by using a lookup table. We only need to store 2^64 booleans in an array first.

[–] recursive_recursion@programming.dev 0 points 2 years ago* (last edited 2 years ago) (1 children)

modulo

pseudocode:

if number % 2 == 0
  return "number is even" (is_num_even = 1 or true)
else
  return "number is odd" (is_num_even = 0 or false)

plus you'd want an input validation beforehand

[–] mac@programming.dev 0 points 2 years ago* (last edited 2 years ago) (1 children)

who needs modulo when you can get less characters out of

while (number > 1) {
  number -= 2;
}
return number;

very efficient

edit: or theres the trusty iseven api

[–] nullPointer@programming.dev 0 points 2 years ago (1 children)

here is somewhat less:

return (number % 2) == 0;

[–] pivot_root@lemmy.world 1 points 2 years ago (1 children)

return !(number & 1);

[–] venoft@lemmy.world 1 points 2 years ago* (last edited 2 years ago) (1 children)

This is the way. Modulo takes too long to compute, bitwise compare should be a lot faster.

return !(number & 0x1);
[–] recursive_recursion@programming.dev 1 points 2 years ago* (last edited 2 years ago)

oh shit yo

this comment chain is pretty awesome, I learned a lot from this thanks!