[LeetCode] Unique Paths II

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.

Solutions:

class Solution {

public:

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

        if(obstacleGrid.size() < 1) return 0;

        int m = obstacleGrid.size(), n = obstacleGrid[0].size();

        int **paths = new int*[m];

        for(int i = 0;i < m;i++)

        {

            paths[i] = new int[n];

            memset(paths[i], 0, n * sizeof(int));

        }

        

        for(int i = 0;i < m;i++)

        {

            for(int j = 0;j < n;j++)

            {

                if(i == 0 && j == 0)

                    paths[i][j] = 1 - obstacleGrid[i][j];

                else if(obstacleGrid[i][j] == 1) 

                    paths[i][j] = 0;

                else

                {

                    if(i - 1 < 0) 

                    {

                        if(j - 1 < 0)

                            paths[i][j] = 0;

                        else

                            paths[i][j] = paths[i][j - 1];

                    }

                    else

                    {

                        if(j - 1 < 0)

                            paths[i][j] = paths[i - 1][j];

                        else

                            paths[i][j] = paths[i - 1][j] + paths[i][j - 1];

                    }

                }

            }

        }

        return paths[m - 1][n - 1];

    }

};