Leetcode 63 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.

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.

先把两条边初始化了然后dp

class Solution(object):
    def uniquePathsWithObstacles(self, ob):
        m, n = len(ob), len(ob[0])       
        dp = [[0 for i in range(n)] for j in range(m)]
        
        for i in range(m):
            if ob[i][0]: break
            dp[i][0] = 1
        for j in range(n):
            if ob[0][j]: break
            dp[0][j] = 1
        
        for i in range(1,m):
            for j in range(1,n):
                if ob[i][j]:
                    continue
                dp[i][j] = dp[i-1][j] + dp[i][j-1]
        return dp[-1][-1]