Leetcode-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.

Analysis:

DP problem. Similiar to Unique Path I.

Solution:

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int[][] grid = obstacleGrid;
        int xLen = grid.length;
        if (xLen==0) return 0;
        int yLen = grid[0].length;
        if (yLen==0) return 0;
        
        int[] path = new int[yLen];
        if (grid[0][0]==1)
            return 0;
        else path[0] = 1;
        for (int i=1;i<yLen;i++)
           if (grid[0][i]==1) path[i]=0;
           else path[i] = path[i-1];
        
        for (int i=1;i<xLen;i++){
            if (grid[i][0]==1) path[0] = 0;
            for (int j=1;j<yLen;j++)
                if (grid[i][j]==1) path[j] = 0;
                else path[j] = path[j-1]+path[j];
        }
        return path[yLen-1];              
        
    }
}