leetcode Unique Paths II

Unique Paths II  原题地址：
https://oj.leetcode.com/problems/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.
加了障碍。
没有到达障碍的路。

public class Solution {
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
if (obstacleGrid[m-1][n-1] == 1)
return 0;
int[][] paths = new int[m]
;
paths[m-1][n-1] = 1;
for (int i = m-2; i >= 0; i--) {
if (obstacleGrid[i][n-1] == 0)
paths[i][n-1] = paths[i+1][n-1];
else
paths[i][n-1] = 0;
}
for (int j = n-2; j >= 0; j--) {
if (obstacleGrid[m-1][j] == 0)
paths[m-1][j] = paths[m-1][j+1];
else
paths[m-1][j] = 0;
}
for (int i = m-2; i >= 0; i--)
for (int j = n-2; j >= 0; j--)
if (obstacleGrid[i][j] == 0)
paths[i][j] = paths[i+1][j] + paths[i][j+1];
else
paths[i][j] = 0;
return paths[0][0];
}
}