# LeetCode – Unique Paths II (Java)

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.

Java Solution

```public int uniquePathsWithObstacles(int[][] obstacleGrid) { if(obstacleGrid==null||obstacleGrid.length==0) return 0;   int m = obstacleGrid.length; int n = obstacleGrid[0].length;   if(obstacleGrid[0][0]==1||obstacleGrid[m-1][n-1]==1) return 0;     int[][] dp = new int[m][n]; dp[0][0]=1;   //left column for(int 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(int 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(int i=1; i<m; i++){ for(int 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]; }```
Category >> Algorithms >> Interview
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