LeetCode: Unique Paths II 解題報告

Unique Paths II

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Question  Solution 

 

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.

 

SOULUTION 1:

跟LeetCode: Unique Paths 解題報告 相比，只不過是判斷一下當前是否是block，若是是block,直接設置D[i][j] 是0就行了 也就是不可達。 一樣在3分鐘以內Bug free 秒答，哦耶！

 1 public class Solution {
 2     public int uniquePathsWithObstacles(int[][] obstacleGrid) {
 3         // 1150
 4         if (obstacleGrid == null || obstacleGrid.length == 0 || obstacleGrid[0].length == 0) {
 5             return 0;
 6         }
 7         
 8         int rows = obstacleGrid.length;
 9         int cols = obstacleGrid[0].length;
10         
11         int[][] D = new int[rows][cols];
12         
13         for (int i = 0; i < rows; i++) {
14             for (int j = 0; j < cols; j++) {
15                 D[i][j] = 0;
16                 if (obstacleGrid[i][j] == 1) {
17                     D[i][j] = 0;
18                 } else {
19                     if (i == 0 && j == 0) {
20                         D[i][j] = 1;
21                     }
22                     
23                     if (i != 0) {
24                         D[i][j] += D[i - 1][j];
25                     }
26                     
27                     if (j != 0) {
28                         D[i][j] += D[i][j - 1];
29                     }
30                 }
31             }
32         }
33         
34         return D[rows - 1][cols - 1];
35     }
36 }

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