Unique Paths II

Posted 2020-06-29 YuriFLAG

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         if (obstacleGrid == null || obstacleGrid.length == 0 || obstacleGrid[0].length== 0) {
 4             return 0;
 5         }
 6         
 7         int n = obstacleGrid.length;
 8         int m = obstacleGrid[0].length;
 9         int[][] paths = new int[n][m];
10         
11         for (int i = 0; i < n; i++) {
12             if (obstacleGrid[i][0] != 1) {
13                 paths[i][0] = 1;
14             } else {
15                 break;
16             }
17         }
18         
19         for (int i = 0; i < m; i++) {
20         if (obstacleGrid[0][i] != 1) {
21                 paths[0][i] = 1;
22             } else {
23                 break;
24             }
25         }
26         
27         for (int i = 1; i < n; i++) {
28             for (int j = 1; j < m; j++) {
29                 if (obstacleGrid[i][j] != 1) {
30                     paths[i][j] = paths[i - 1][j] + paths[i][j - 1];
31                 } else {
32                     paths[i][j] = 0;
33                 }
34             }
35         }
36         return paths[n - 1][m - 1];
37     }
38 }