HI guys, I was wandering if some of you know some good resources online to practice the Recursion tree method for estimating the Big-O for recursion functions?, I'm familiar with the concept but I'm a little rusty :D , so a good amount of solved example to try out would be a great thing :) ..

I tried google, but all I can come up with was either explaining the concept like this and this or just a lot of unsolved examples like this .

any links would be appreciated :) ..

side note: while trying solving a problem here @ codeforces, I wasn't able to estimate my running time correctly here http://codeforces.me/contest/559/submission/21233079 , so if anyone wants to help out explaining the big-O here that would be great :) ..

For a while now I can't open any AC codes for a given problem!, not even mine!!

what could I do to fix it?