If you actually tried to see if someone else asked the same question, you'd find this blog on the top of "Recent actions". It's pretty much the same thing, and there are some explanations in the comments.

As to implementation: you should try to make your own. Everyone has a different coding style, and it's best to understand what every part of your code does, for when you need to modify it for more advanced problems.

I'm using non-recursive segment tree in my solution, which is faster than recursive one. It doesn't support range updates and range queries at the same time, though.