Coding Paths in Blocked Grid

MediumPython

Problem

Consider a matrix of m by n sized grid where some cells are blocked. How many possible paths from start to finish are there?

Assume the start is the top-left cell and the finish is the bottom-right cell. A valid path moves only right or down and cannot enter a blocked cell. Implement count_paths(grid), where grid is a rectangular matrix containing 0 for open cells and 1 for blocked cells; return the number of valid paths as an integer.

Constraints

1 <= m, n <= 100
grid has m rows and n columns
grid[r][c] is either 0 for open or 1 for blocked
Moves are restricted to right and down

Function Signature

def count_paths(grid):

CodePython 3

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