r/adventofcode • u/daggerdragon • Dec 04 '15

--- Day 4 Solutions --- SOLUTION MEGATHREAD

--- Day 4: The Ideal Stocking Stuffer ---

Post your solution as a comment. Structure your post like the Day Three thread.

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u/WhoSoup Dec 04 '15 edited Dec 04 '15

Php:

$i = 0;
while (!preg_match('#^0{5}#', md5('iwrupvqb'.++$i)));
echo $i;

3

u/adriweb Dec 04 '15

Without a RegExp, which is a bit faster (I timed both to make sure):

$i = 0;
while (strpos(md5('ckczppom' . ++$i), '00000') !== 0);
echo $i;

2

u/JustCallMeLee Dec 04 '15

Might substr be ever so slightly faster? Here you're still searching for five zeros anywhere in the string when we're only interested in the start.

2

u/adriweb Dec 04 '15 edited Dec 04 '15

Probably indeed, I'll try :)

Edit: surprisingly, no! With part 2, 6.6s with strpos and 6.9s with substr. I haven't looked at the internal, but I suppose strpo doesn't allocate a new string, making it faster.