LeetCode: Unique Paths II 解题报告

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 解题报告 相比，只不过是判断一下当前是不是block，如果是block,直接设置D[i][j] 是0就好了 也就是不可达。 同样在3分钟之内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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