LeetCode OJ 系列之63 Unique Paths II --Python

Problem:

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.

Answer:

class Solution(object):    def uniquePathsWithObstacles(self, obstacleGrid):        """        :type obstacleGrid: List[List[int]]        :rtype: int        """        if obstacleGrid[-1][-1]==1:return 0                for i in range(len(obstacleGrid)):            for j in range(len(obstacleGrid[i])):                if obstacleGrid[i][j]==1:                    obstacleGrid[i][j]=-1                elif i==0 and j==0:                    obstacleGrid[i][j]=1                elif i==0:                    if obstacleGrid[i][j-1]==-1 or obstacleGrid[i][j-1]==0:obstacleGrid[i][j]=0                    else : obstacleGrid[i][j]=1                elif j==0:                    if obstacleGrid[i-1][j]==-1 or obstacleGrid[i-1][j]==0:obstacleGrid[i][j]=0                    else : obstacleGrid[i][j]=1                else:                    if obstacleGrid[i][j-1]==-1 and obstacleGrid[i-1][j]==-1:obstacleGrid[i][j]=0                    elif obstacleGrid[i][j-1]==-1:obstacleGrid[i][j]=obstacleGrid[i-1][j]                    elif obstacleGrid[i-1][j]==-1:obstacleGrid[i][j]=obstacleGrid[i][j-1]                    else :obstacleGrid[i][j]=obstacleGrid[i-1][j]+obstacleGrid[i][j-1]                            return obstacleGrid[-1][-1]