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.

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 n = obstacleGrid.length;        int m = obstacleGrid[0].length;        int[][] paths = new int[n][m];        for (int i = 0; i < n; i++) {            if (obstacleGrid[i][0] != 1) {                paths[i][0] = 1;            } else {                break;            }        }        for (int i = 0; i < m; i++) {            if (obstacleGrid[0][i] != 1) {                paths[0][i] = 1;             } else {                break;            }        }        for (int i = 1; i < n; i++) {            for (int j = 1; j < m; j++) {                if (obstacleGrid[i][j] != 1) {                    paths[i][j] = paths[i - 1][j] + paths[i][j - 1];                } else {                    paths[i][j] = 0;                }            }        }        return paths[n - 1][m - 1];    }}