leetcode 23 不同路徑2

dfs + 打表過不了，只能動態規劃 

int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        if (!obstacleGrid.size() || !obstacleGrid[0].size()) 
            return 0;
        int rows = obstacleGrid.size(), cols = obstacleGrid[0].size();
        vector<vector<long long>> dp(rows, vector<long long>(cols, 0));
        if (obstacleGrid[0][0] == 1) 
            return 0;
        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j < cols; j++)
            {
                if (obstacleGrid[i][j] == 1) 
                    continue;
                if (i == 0 && j == 0)
                    dp[0][0] = 1;
                else if (i == 0)
                    dp[i][j] = dp[i][j - 1];
                else if (j == 0)
                    dp[i][j] = dp[i - 1][j];
                else
                    dp[i][j] = dp[i][j - 1] + dp[i - 1][j];
            }
        }
        return dp[rows - 1][cols - 1];
    }