Unique Path II

Problem: Unique Path II

We can basically use solution to Unique Path, except for position with obstacle there's no solution, which means 0.

Code in Python:

class Solution(object):
    def uniquePathsWithObstacles(self, obstacleGrid):
        """
        :type obstacleGrid: List[List[int]]
        :rtype: int
        """
        if obstacleGrid[0][0] == 1: return 0

        m, n = len(obstacleGrid), len(obstacleGrid[0])
        dp = [[0] * n for _ in xrange(m)]

        dp[0][0] = 1
        for i in xrange(1, m):
            dp[i][0] = 0 if obstacleGrid[i][0] else dp[i-1][0]
        for j in xrange(1, n):
            dp[0][j] = 0 if obstacleGrid[0][j] else dp[0][j-1]

        for i in xrange(1, m):
            for j in xrange(1, n):
                dp[i][j] = 0 if obstacleGrid[i][j] else dp[i-1][j] + dp[i][j-1]

        return dp[-1][-1]