Sum of Matrix After Queries - Solution & Explanation

Instead of updating a full matrix, which could be inefficient considering the constraints, we simulate the updates using arrays to keep track of row and column updates. This avoids the need to modify the entire matrix, thus saving computation time and space.

This solution uses two arrays, one for row updates and another for column updates, to store the latest query operation on each row and column. The arrays row_updates and col_updates record the index of the last query that affected each row or column. The computation of the final matrix sum happens by choosing the latest applicable query update for each cell.

By processing the queries in reverse order, we can efficiently manage the rows and columns to prevent unnecessary overwrites. By using flags to record rows and columns that have already been set, we can avoid redundant operations and achieve an optimized simulation.

This JavaScript solution processes queries in reverse to track which rows and columns have been set. By using boolean arrays to mark applied operations, we accumulate sums only for the first (in reverse order) applicable update, thus minimizing redundant calculations.