dsa · medium

Unique Paths II

A robot starts at the top-left of obstacleGrid and may only move right or down. Cells with 1 are blocked. Return how many paths reach the bottom-right. If start or end is blocked, the answer is 0.

Arguments

• obstacle_grid — m×n grid; 1 is blocked, 0 is open

Example

[[0,0,0],[0,1,0],[0,0,0]] has one blocked cell in the middle. There are 2 paths around it.

Constraints

1 <= m, n <= 100 obstacleGrid[i][j] is 0 or 1 Hidden tests include near-max size for this bound; a slower-than-intended solution TLEs.

Examples

Example 1

Input:
[[0,0,0],[0,1,0],[0,0,0]]

Expected:
2

Example 2

Input:
[[0,1],[0,0]]

Expected:
1

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