1         public static int UniquePathsIIDP(List<List<int>> obstacleGrid)
 2         {
 3             int m = obstacleGrid.Count;
 4             int n = obstacleGrid[0].Count;
 5             int[,] grid = new int[m, n];
 6 
 7             // if the start point is a obstacle, return 0
 8             if (obstacleGrid[0][0] == 1)
 9                 return 0;
10             grid[0, 0] = 1;
11 
12             for (int i = 1; i < m; i++)
13             {
14                 if (obstacleGrid[i][0] == 0 && grid[i - 1, 0] != 0)
15                     grid[i, 0] = 1;
16                 else
17                     grid[i, 0] = 0;
18             }
19 
20             for (int i = 1; i < n; i++)
21             {
22                 if (obstacleGrid[0][i] == 0 && grid[0, i - 1] != 0)
23                     grid[0, i] = 1;
24                 else
25                     grid[0, i] = 0;
26             }
27 
28             for (int i = 1; i < m; i++)
29             {
30                 for (int j = 1; j < n; j++)
31                 {
32                     if (obstacleGrid[i][j] == 1)
33                         grid[i, j] = 0;
34                     else
35                         grid[i, j] = grid[i - 1, j] + grid[i, j - 1];
36                 }
37             }
38 
39             return grid[m - 1, n - 1];
40         }