Re: recursion question

On Wed, 30 Aug 2000, Robert J. Cissell wrote: > I'm trying to write my first recursive function but I'm not doing too well. I have a > mysql database with the fields of topic_id, topic_name, and parent_topic_id. If I have a topic_id > with a parent_topic_if of 5, I want the function to get the topic_name and parent_topic_id for 5, > and again and again until it reaches a parent_topic_id of 0, which would be my top level. As it > goes, it would store these values in an array which I can run through later to build a path from the > top to whatever topic_id i started out at. What I can't figure is how to set up the recursive > function to do so. I have no problem with the database stuff, but I need help with the function > stuff. Any ideas or suggestions are greatly appreciated. > > Robert Cissell > In this case, and in most cases in a production environment, I would stay away from recursion unless you know exactly what you're doing; anything you can do recursively you can also do iteratively. My suggestion is to use a while loop in this case and store the path as you go. In any case, for any recursive function, you need a base case -- the thing you're looking for at the end of the recursion; and then you need a recursive call. For instance, I have a site tree object which is a real n-ary tree. Here's how I get the path for a node. function rec_getPath($node) { // base case - level 0 - root of the tree if($node->level == 0) { return $node->getPath(); } // recursive case -- get the parent's path and then node's path. return $node->getParent()->getPath() . $node->getPath(); } Dean Hall.