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.

 1 public class Solution {
 2     public int uniquePathsWithObstacles(int[][] obstacleGrid) {
 3         int m = obstacleGrid.length;
 4         int n = obstacleGrid[0].length;
 5         if (m == 0 || n == 0) return 0; 
 6         if (obstacleGrid[0][0] == 1 || obstacleGrid[m-1][n-1] == 1) return 0;
 7         int[][] matrix = new int[m][n];
 8         return FindPath(m-1, n-1, obstacleGrid, matrix);
 9     }
10     
11     public int FindPath(int i, int j, int[][] obstacleGrid, int[][] matrix) {
12         if (matrix[i][j] != 0) return matrix[i][j];
13         if (i == 0 && j == 0) return 1;
14         if (i == 0 && j != 0 && obstacleGrid[i][j] != 1) {
15             matrix[i][j] = FindPath(i, j-1, obstacleGrid, matrix);
16             return matrix[i][j];
17         }
18         if (i != 0 && j == 0 && obstacleGrid[i][j] != 1) {
19             matrix[i][j] = FindPath(i-1, j, obstacleGrid, matrix);
20             return matrix[i][j];
21         }
22         if (i != 0 && j != 0 && obstacleGrid[i][j] != 1) {
23             matrix[i][j] = FindPath(i, j-1, obstacleGrid, matrix) + FindPath(i-1, j, obstacleGrid, matrix);
24             return matrix[i][j];
25         }
26         else return 0;
27     }
28 }