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