63. Unique Paths II (Graph; DP)

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.

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
        int m = obstacleGrid.size();
        int n = obstacleGrid[0].size();
        int dp[m][n];
        
        if(obstacleGrid[0][0] == 1) return 0;
        dp[0][0] = 1;
        for(int i = 1; i< n; i++ )
        {
            if(obstacleGrid[0][i] == 1) dp[0][i] = 0;
            else dp[0][i] = dp[0][i-1];
        }
        for(int i = 1; i< m; i++ )
        {
            if(obstacleGrid[i][0] == 1) dp[i][0] = 0;
            else dp[i][0] = dp[i-1][0];
        }
        
        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];
    }
};