Talk:Happy numbers

On caching (and laziness)

It seemed prudent to put in simple caching of n in the Python solution, but not the full-length permutations of the digits of n as cache size grows very quickly. I had thought of just putting in a 'normal form' of n into the cache which would be the digits in sorted order, but then you would have to calculate the normal form before every search of the cache, which would take more time. Time vs space, space vs time? I chose the lazy option and left them both out of the Python, but maybe I should add an example with the normal-form space optimised cache so an implementation is out there? --Paddy3118 00:28, 7 May 2009 (UTC)