Problem - Range Sum Query 2D Mutable

Given a 2D matrix, implement:

• update(row, col, val): Update matrix[row][col] to val
• sumRegion(row1, col1, row2, col2): Return sum of rectangle You're solving the same problem from segment trees, but 2D BIT is simpler to implement. Constraints: matrix up to $200 \times 200$, up to $10^4$ operations.