Leetcode 63 Unique Paths II

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.

Note: m and n will be at most 100.

Solution 1: when i==0 or j==0, if it s blocked then following will be 0 path as well. Pay attention the differences from Leetcode 62.

 public class Solution {  
   public int uniquePathsWithObstacles(int[][] obstacleGrid) {  
     int m=obstacleGrid.length;  
     if (m==0) return 0;  
     int n=obstacleGrid[0].length;  
     if (n==0) return 0;  
     int[] dp= new int[n];  
     for (int i=0; i<m; i++) {  
       for (int j=0; j<n; j++) {  
         if (obstacleGrid[i][j]==1) dp[j]=0;  
         else if (i==0) {  
           if (j==0) dp[j]=1;  
           else dp[j]=dp[j-1];  
         }  
         else if (j==0) dp[j]=dp[j];  
         else dp[j]=dp[j-1]+dp[j];  
       }  
     }  
     return dp[n-1];  
   }  
 }