I want to become a more skilled programmer. I also want to do it through Objective-C and iOS. What websites or programs that you know of have problems that I can solve (with the answers)? I have failed some programming tests for jobs (such as "Given 2 values in a Binary Tree - how do you find the lowest common ancestor?) and I want to become a better engineer. I have developed 54 iOS/Android apps to date, but my core CS Skills apparently are rusty/bad. I have looked at TopCoder - but there aren't very many competitions going on, the website is terrible, and there does not appear to be anything that really supports Objective-C/iOS Websites?