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.
Solution:
Code:

<span style="font-size:14px;">class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
const int m = obstacleGrid.size();
if (m == 0) return 0;
const int n = obstacleGrid[0].size();
if (obstacleGrid[0][0] == 1) return 0;
else obstacleGrid[0][0] = 1;
for (int i = 1; i < m; ++i)
if (obstacleGrid[i][0] == 1) obstacleGrid[i][0] = 0;
else obstacleGrid[i][0] = obstacleGrid[i-1][0];
for (int j = 1; j < n; ++j)
if (obstacleGrid[0][j] == 1) obstacleGrid[0][j] = 0;
else obstacleGrid[0][j] = obstacleGrid[0][j-1];
for (int i = 1; i < m; ++i)
for (int j = 1; j < n; ++j)
if (obstacleGrid[i][j] == 1) obstacleGrid[i][j] = 0;
else obstacleGrid[i][j] = obstacleGrid[i-1][j]+obstacleGrid[i][j-1];
return obstacleGrid[m-1][n-1];
}
};</span>