hacker.org

solved it with straight forward algorithm with 300 LoC in java.
I've implemented backtracking functionality, but my first choice was always correct so that no backtracking was done
running time with GUI was several seconds.

I found the path using dijkstra's algorithm optimized with binary heaps, which finds the shortest path between two points given a graph. The graph was not hard to construct and the most important thing was to set the cost of black points to infinity.

I guess not, therefore the reverse calculation is only about twice as fast as the normal brute force approach. Well, what you have to solve is the linear congruence equation: x*22233442 == 186968300 (mod 4294967296). This can be done with knowledge of elementary number theory (extended euclidean al...

to the confused ones:
when someone wins, all the succeeding moves should be ignored.

xotihcan wrote:Obiously it can be made at any hour... But, i dont know how to tell the script (chal.php) the time i want...

your time means nothing to the server.

PeterS wrote:Ok, I finally got it. Try rounding to the sixth decimal digit.
This is odd since the wikipedia article says, the precision is about 7.225 decimal digits.

you're right, it can hold 7 decimal digits.
but have you forgot the one digit to the left of the point?

sabretooth wrote:

ftfish wrote:i tried a time machine, but all i could get is the list of top10(or 11?), i've no further idea about how i can get the 15th hacker.... any hints please? thanks

did it say the 15th hacker? read it again

ehhh.. my foolish eyes... thanks

i also did it by searching for png headers.
i know i can open the file with wireshark, but i wonder how i can use wireshark to get the answer.
could you please give me a instruction? thanks!

my first thought was to perform a brute force substitution, but the size of the image is too large. so i had to checkout wiki for specifications of png format. after knowing a bit of the structure of png, i tried to trace the Python Imaging Lib reading that png file. when an error comes, the lib is ...

i tried a time machine, but all i could get is the list of top10(or 11?), i've no further idea about how i can get the 15th hacker.... any hints please? thanks

sorry for being spoiler

I used the fact: when a<b, a/b equals 0.
max(a,b)=(a/b *a + b/a *b)/(a/b + b/a)

here's my code: