unique-paths-ii.py

class Solution:
    def uniquePathsWithObstacles(self, obstacleGrid: List[List[int]]) -> int:
        if obstacleGrid[0][0] == 1 or obstacleGrid[-1][-1] == 1:
            return 0
        m, n = len(obstacleGrid), len(obstacleGrid[0])
        dp = [0] * n
        dp[0] = 1
        for i in range(m):
            if obstacleGrid[i][0] == 1:
                dp[0] = 0
            for j in range(1, n):
                if obstacleGrid[i][j] == 0:
                    dp[j] = dp[j] + dp[j - 1]
                else:
                    dp[j] = 0
        return dp[-1]