Range Sum Query 2D - Mutable : Past Google Coding Interview
Problem
https://leetcode.com/problems/range-sum-query-2d-mutable/
How to Solve
This problem can be solved by using Binary Indexed Tree. Please check below article if you want to know the details of Binary Indexed Tree.
keita-matsushita.hatenablog.com
But in this problem case, I use BIT(Binary Indexed Tree) as a 2D because input values is a matrix.