unique_path_II.py

class Solution(object):
    def uniquePathsWithObstacles(self, obstacleGrid):
        """
        :type obstacleGrid: List[List[int]]
        :rtype: int
        """
        
        if len(obstacleGrid) <= 0:
            return 0
        
        
        
        dp = [[0 for i in range(len(obstacleGrid[0]))] for j in range(len(obstacleGrid))]
        if obstacleGrid[0][0] == 1:
            dp[0][0] = 0
        else:
            dp[0][0] = 1
        
        for i in range(1, len(obstacleGrid[0])):
            if obstacleGrid[0][i] == 1:
                dp[0][i] = 0
            else:
                dp[0][i] += dp[0][i-1]
                
                
        for i in range(1, len(obstacleGrid)):
            if obstacleGrid[i][0] == 1:
                dp[i][0] = 0
            else:
                dp[i][0] += dp[i-1][0]
        
       
        for i in range(1, len(obstacleGrid)):
            for j in range(1, len(obstacleGrid[0])):
                if obstacleGrid[i][j] == 1:
                    dp[i][j] = 0
                    continue
                else:
                    dp[i][j] = dp[i-1][j] + dp[i][j-1]
            
        
        return dp[len(obstacleGrid)-1][len(obstacleGrid[0])-1]