Here are iterative solutions to Nick Parlante's binary tree problems. Recursive solutions are quite common, but recursion is sometimes not practical due to stack overflows. Some compilers can optimize for tail recursion, so it depends on your needs. Many of the algorithms are complex and one of them (Print tree as sorted list) needs to be reworked for better optimization, but in general, these solutions can provide you with a stepping stone to understanding iterative binary tree solutions.