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 is2.
Note: m and n will be at most 100.

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