August 24, 2018

Coin flip coding golf

A short coding golf snippet for a simple coin flip.

Full code

//generate a cryptographically secure pseudo-random string
$randomString = bin2hex(random_bytes(16));
//select the first char
$randomChar = substr($randomString,0,1);
//if this char is a number, use it
if(is_numeric($randomChar)){
    $randomNumber = $randomChar;
}
//if not, use the numeric representation
else {
    $randomNumber = strpos('abcdefghijklmnopqrstuvwxyz',$randomChar);
}
//check if the number is odd or even
$numericBoolean = $randomNumber % 2;
//odd = heads, even = tails
echo ($numericBoolean==1?'heads':'tails');

Shorted version

$a = substr(bin2hex(random_bytes(16)),0,1);
echo (((is_numeric($a)?$a:strpos('abcdefghijklmnopqrstuvwxyz',$a))%2)==1?'heads':'tails');

The code still feels far too long for such a simple task. The first thing I don’t like is the whole ABC string. So instead of checking if the first char is a number or not and then get the numeric value of a letter, I could just get the ASCII value of that character - regardless if it is a number or not.

I now can shorten the code to this:

echo ord(substr(bin2hex(random_bytes(16)),0,1))%2?'heads':'tails’;

But instead of using an alphanumeric value when I only need a number is still a bit of an overkill. So this time I am going to use the function random_int, which I already wrote about in a previous post[1].

echo random_int(PHP_INT_MIN,PHP_INT_MAX)%2?'heads':'tails’;

What if I just want a random boolean? I could get just that and pass 0 and 1 as the range.

echo random_int(0,1)?'heads':'tails';

This is IMHO the shortest most random possible coin flip solution.

Sources:

[1] https://blog.cipher.digital/article/php7-csprng

Tags: php, coding golf

« back

010100100110000101101110011001000110111101101101010000110110100101110000011010000110010101110010

About the author

human, software engineer, tech enthusiast, security researcher

E-Mail: blog@cipher.digital