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