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.

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        
        if(obstacleGrid == null || obstacleGrid.length == 0 || obstacleGrid[0].length == 0){
            return 0;
        }
        
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        
        int[][] dp = new int[m][n];
        
        for(int i = 0; i < n; i++){
            if(obstacleGrid[0][i] == 0){
                dp[0][i] = 1;
            }else{
                break;
            }
        }
        
        for(int j = 0; j < m; j++){
            if(obstacleGrid[j][0] == 0){
                dp[j][0] = 1;
            }else{
                break;
            }
        }
        
        for(int i = 1; i < m; i++ ){
            for(int j = 1; j < n; j++){
                if(obstacleGrid[i][j] == 1){
                    dp[i][j] = 0;
                }else{
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        
        return dp[m - 1][n - 1];
    }
}