Unique Paths II

Source

• lintcode: Unique Paths II

Follow up for "Unique Paths":

Now consider if some obstacles are added to the grids. How many unique paths would there be?

An obstacle and empty space is marked as 1 and 0 respectively in the grid.

Example
For example,
There is one obstacle in the middle of a 3x3 grid as illustrated below.

[
  [0,0,0],
  [0,1,0],
  [0,0,0]
]
The total number of unique paths is 2.

Note
m and n will be at most 100.

Python

class Solution:
    """
    @param obstacleGrid: An list of lists of integers
    @return: An integer
    """
    def uniquePathsWithObstacles(self, obstacleGrid):
        # write your code here
        m = len(obstacleGrid)
        n = len(obstacleGrid[0])
        row=[0]*m
        row[0]=1

        for i in range(n):
            for j in range(m):
                if obstacleGrid[j][i]==1:
                    row[j]=0
                elif j>0:
                    row[j]+=row[j-1]
        return row[m-1]