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`

.Analysis:

Just a little bit changes from the previous problem.

Note that if the start position is obstacle, then return 0.

Pretty easy if you solve the previous one.

Code:

class Solution { public: int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) { // Start typing your C/C++ solution below // DO NOT write int main() function int m = obstacleGrid.size(); int n = obstacleGrid[0].size(); vector<vector<int> > arr(m,vector<int>(n,0)); if (obstacleGrid[0][0]==1){return 0;} arr[0][0]=1; for (int i=1;i<m;i++){ if (obstacleGrid[i][0]!=1){ arr[i][0] = arr[i-1][0]; } } for (int i=1;i<n;i++){ if (obstacleGrid[0][i]!=1){ arr[0][i] = arr[0][i-1]; } } for (int i=1;i<m;i++){ for(int j=1;j<n;j++){ if (obstacleGrid[i][j]!=1){ arr[i][j] = arr[i][j-1] + arr[i-1][j]; } } } return arr[m-1][n-1]; } };

what is the space complexity ? thank you :)

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