[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.

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