63. Unique Paths II

Practice Unique Paths II for free on NudgeCode: Medium, Dynamic Programming pattern. Write it in Python or JavaScript, run the tests in your browser, and ask for a hint when you are stuck.

A robot starts at the top-left cell of a grid and wants to reach the bottom-right cell, moving only right or down. Cells marked 1 are blocked and cells marked 0 are open. Return how many different routes avoid every blocked cell.

Example

obstacleGrid = [[0,0,0],
                [0,1,0],
                [0,0,0]]   ->  2
obstacleGrid = [[0,1],[0,0]]  ->  1

Constraints

• 1 <= rows, cols <= 100
• Each cell is 0 or 1
• The answer fits in a 32-bit signed integer