Unique Paths II

There is one obstacle in the middle of a 3x3 grid as illustrated below.

[
  [0,0,0],
  [0,1,0],
  [0,0,0]
]

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int len = obstacleGrid.length;
        if(len==0) return 0;
        int len2 = obstacleGrid[0].length;
        if(obstacleGrid[0][0]==1) return 0;
        int[] max = new int [len2];
        max[0] =1;
        for(int i=0;i<len;i++){
            for(int j=0;j<len2;j++){
                if(obstacleGrid[i][j]==1)
                    max[j]=0;
                else if(j>0){
                    max[j] = max[j]+max[j-1];
                }
            }
        }
        return max[len2-1];
    }
}