Question: Given a grid of size m * n, lets assume you are starting at (1,1) and your goal is to reach (m,n). At any instance, if you are on (x,y), you can either go to (x, y + 1) or (x + 1, y). Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid.