[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.

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
        int m = obstacleGrid.size(), n = obstacleGrid[0].size();
        vector<vector<int>> f(m, vector<int>(n, 0));
        for(int i = 0; i < m; i++)
        {
            if(obstacleGrid[i][0] == 0)
                f[i][0] = 1;
            else
                break;
        }
        for(int i = 0; i < n; i++)
        {
            if(obstacleGrid[0][i] == 0)
                f[0][i] = 1;
            else
                break;
        }
        for(int i = 1; i < m; i++)
        {
            for(int j = 1; j < n; j++)
            {
                if(obstacleGrid[i][j] == 0)
                    f[i][j] = f[i-1][j] + f[i][j-1];
                else
                    f[i][j] = 0;
            }
        }
        return f[m-1][n-1];
    }
};