Hello Codeforces!
I implemented a solution with a range tree as bmerry explains here.
It passes the 3 first subtasks but I get Memory Limit on the 2 last subtasks, though I'm using a sparse segment tree.
I store the tree with pointers (each Node has pointers to left son and right son).
I only allocate memory for a node if it is visited during an update.
If I arrive to a node which doesn't exist during a query, I don't create it, I just return 0 (because all the elements covered by this node are zeroes).
So, my memory complexity is O(logR·logC·Nu), which seems to be too big :'( Do you have a trick to reduce the ML ?
