### Problem

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

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.

### JavaScript Code

```function uniquePathsWithObstacles(obstacleGrid) {
if(obstacleGrid==null||obstacleGrid.length==0)
return 0;

var m = obstacleGrid.length;
var n = obstacleGrid.length;

if(obstacleGrid==1||obstacleGrid[m-1][n-1]==1)
return 0;

var dp = [];
for(var i=0; i<m; i++){
var temp = [];
for(var j=0; j<n; j++){
temp.push(0);
}
dp.push(temp);
}

dp=1;

//left column
for(var i=1; i<m; i++){
if(obstacleGrid[i]==1){
dp[i] = 0;
}else{
dp[i] = dp[i-1];
}
}

//top row
for(var i=1; i<n; i++){
if(obstacleGrid[i]==1){
dp[i] = 0;
}else{
dp[i] = dp[i-1];
}
}

//fill up cells inside
for(var i=1; i<m; i++){
for(var j=1; j<n; j++){
if(obstacleGrid[i][j]==1){
dp[i][j]=0;
}else{
dp[i][j]=dp[i-1][j]+dp[i][j-1];
}
}
}

return dp[m-1][n-1];
}
```

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