Given a grid with $$$R \leq 10^5$$$ rows and $$$C \leq 10^5$$$ columns, there are $$$Q \leq 10^3$$$ obstacles on the grid. You need to find the number of path from $$$(1, 1)$$$ to $$$(R, C)$$$ that do not go through any obstacle.

I created a video on this classical problem https://youtu.be/i74DlMrPuQk

Practice Problem