Showing posts with label chinese remainder theorem. Show all posts
Showing posts with label chinese remainder theorem. Show all posts

Sunday, August 4, 2013

project euler problem 271

Modular Cubes, part 1

This problem is simple. But pure brute force is not an option.  I checked my old code, I kept a list of "possible solutions" and used something like bigInteger to do the modulo work since the numbers are too big.  It only takes 17 ms, not too bad!

This time, I tried to avoid using bigIntegers since most of the problems with a number greater than 150 may be solved without the help of GMP.  I found there is a better solution which used the famous Chinese Remainder Theorem.  The problem is extremely simple after one understand what is going on inside CRT.  Quite a few other project euler problems also check one's understanding of CRT, this one being the simplest one. It is a good opportunity to learn CRT!
My code runs less than 10 ms.