Assign a number (between 1 and 9) to a md5 hash

Question

Having a md5 hash like:

md5("test") = "098f6bcd4621d373cade4e832627b4f6"

How can I write a function to return a number between 1 and 9 every time I pass the md5 hash to it? The number must always be the same, i.e. myfunc("098f6bcd4621d373cade4e832627b4f6") should always return the same number. Thanks for your help.

Answer 1

Return the leftmost digit (in 1..9 of course) in the hash considered as a string.

Or have I missed the point ?

Answer 2

Simplest way: find first number in md5 and return it :) You can do it with easy regexp. Of course remember to have some safe return value if no number was found (but it will happen hardly ever).

Answer 3

Return 1 all the time. Meets the spec!

More seriously, what do you need this number to represent?

Answer 4

This is WAY overkill, and the suggestion of returning left-most digit is the best...

function myfunc($md5) {
    $total = 0;
    foreach (str_split($md5) as $char) $total += ord($char);
    return $total % 9 + 1;
}

echo myfunc("098f6bcd4621d373cade4e832627b4f6");

This way you can easily change the range of return values you are interested in by modifying the return statment.

Or, a more compact version:

function myfunc2($md5) {
    return array_sum(array_map("ord", str_split($md5))) % 9 + 1;
}

You could even pass the min and max as args:

function myfunc2($md5, $min = 1, $max = 9) {
    return array_sum(array_map("ord", str_split($md5))) % $max + $min;
}

myfunc2("098f6bcd4621d373cade4e832627b4f6", 10, 20);

Answer 5

Here's a solution:

return substr(base_convert($md5, 16, 9), -1) + 1;

This is what you probably want although you did not say it.

Answer 6

You essentially want a hash function of your hash function. This would be some psedo code:

int hashhash(string hash)
    return (hash[0] % 9) + 1;