Please Can somebody suggest link to study range update in Sqrt Decomposition Technique?

There was a question in recent Oct challenge which could have been solved by sqrt technique too with range update.

Question

Link : https://www.codechef.com/OCT16/problems/BGQRS

EDIT : I know the basic SQRT Techniique just the range update part as when we update it block by block, the next query which requires us to traverse each element(all in 1 block) then what happens?

Thanks