leetcode 63. 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.

这题的测试好恶心，居然左上角还有1的情况，请问机器人怎么站

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        if(obstacleGrid==null || obstacleGrid.length==0) return 0;
        int w = obstacleGrid.length, h = obstacleGrid[0].length;
        int[][] dp = new int[w][h];
        // dp[0][0] = 1;
        if(obstacleGrid[0][0] ==1) return 0;
        dp[0][0] = 1;
        for(int i=1; i<w; i++){
            if(obstacleGrid[i][0]==1){
                dp[i][0] = 0;
            }else{
                dp[i][0] = dp[i-1][0];
            }
        }

        for(int j=1; j<h; j++){
            if(obstacleGrid[0][j]==1){
                dp[0][j] = 0;
            }else{
                dp[0][j] = dp[0][j-1];
            }
        }

        for(int i=1; i<w; i++){
            for(int j = 1; j<h; j++){
                if(obstacleGrid[i][j]==1){
                    dp[i][j]=0;
                }else{
                    dp[i][j] = dp[i-1][j]+dp[i][j-1];
                }
            }
        }

        return dp[w-1][h-1];
    }
}