Unique Paths II [LeetCode]

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.

Solution: The same to Unique Paths, just add obstacle check.

 1 class Solution {

 2 public:

 3     int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {

 4         if(obstacleGrid.size() <= 0 || obstacleGrid[0].size() <= 0)

 5             return 0;

 6 

 7         int row = obstacleGrid.size();

 8         int column = obstacleGrid[0].size();

 9         vector<int> path_nums(column, 0);

10         for(int i = 0; i < row; i ++) {

11             int row_idx = row - 1 - i;

12             for(int j = 0; j < column; j ++ ) {

13                 int column_idx = column - 1 - j;

14                 if(i == 0 && j == 0 && obstacleGrid[row_idx][column_idx] == 1)

15                     return 0;

16                 if(i == 0 && j == 0 && obstacleGrid[row_idx][column_idx] == 0) {

17                     path_nums[j] = 1;

18                 }else {

19                     if(obstacleGrid[row_idx][column_idx] == 1) {

20                         path_nums[j] = 0;

21                     }else {

22                         if(j != 0)

23                             path_nums[j] += path_nums[j - 1];

24                     }

25                 }

26             } 

27         }

28         return path_nums[column - 1];

29     }

30 };