```
public class Solution {
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
if (obstacleGrid.length == 0 || obstacleGrid[0].length == 0)
return 0;
int m = obstacleGrid.length,
n = obstacleGrid[0].length;
int[][] f = new int[m][n];
int i = 0, j = 0;
while (i < m && obstacleGrid[i][0] == 0) {
f[i][0] = 1;
i ++;
}
while (j < n && obstacleGrid[0][j] == 0) {
f[0][j] = 1;
j ++;
}
for (i = 1; i < m; i ++)
for (j = 1; j < n; j ++)
if (obstacleGrid[i][j] == 0)
f[i][j] = f[i - 1][j] + f[i][j - 1];
return f[m - 1][n - 1];
}
}
```