# Unique Paths II

# Question

http://www.lintcode.com/en/problem/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.

# Example

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.

# Answer

```
class Solution {
public:
/*
* @param obstacleGrid: A list of lists of integers
* @return: An integer
*/
int uniquePathsWithObstacles(vector<vector<int>> &obstacleGrid) {
int m = obstacleGrid.size();
if (m <= 0)
return 0;
int n = obstacleGrid[0].size();
if (obstacleGrid[0][0] == 1 || obstacleGrid[m-1][n-1] == 1)
return 0;
vector<vector<int>> res(m, vector<int>(n, 0));
res[0][0] = 1;
for (int j = 1; j < n; j++) {
if (obstacleGrid[0][j] == 1) {
for (int i = j; i < n; i++)
res[0][i] = 0;
break;
} else
res[0][j] = 1;
}
for (int j = 1; j < m; j++) {
if (obstacleGrid[j][0] == 1) {
for (int i = j; i < m; i++)
res[i][0] = 0;
break;
} else {
res[j][0] = 1;
}
}
for (int i = 1; i < m; i++) {
for (int j = 1; j < n; j++) {
if (obstacleGrid[i][j] == 1)
res[i][j] = 0;
else
res[i][j] = res[i-1][j] + res[i][j-1];
}
}
return res[m-1][n-1];
}
};
```