class Solution {
public:
    /**
     * @param obstacleGrid: A list of lists of integers
     * @return: An integer
     */ 
    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
        // write your code here
        int row = obstacleGrid.size();
        if (row == 0) {
            return 0;
        }
        int col = obstacleGrid[0].size();
        if (col == 0) {
            return 0;
        }

        vector<vector<int>> res(row, vector<int>(col, 0));

        for (int i = 0; i < row; i++) {
            if (obstacleGrid[i][0] == 1) {
                for (int j = i; j < row; j++) {
                    res[j][0] = 0;
                }
                break;
            } else {
                res[i][0] = 1;
            }
        }

        for (int j = 0; j < col; j++) {
            if (obstacleGrid[0][j] == 1) {
                for (int i = j; i < col; i++) {
                    res[0][i] = 0;
                }
                break;
            } else {
                res[0][j] = 1;
            }
        }

        for (int i = 1; i < row; i++) {
            for (int j = 1; j < col; j++) {
                if (obstacleGrid[i][j] == 1) {
                    res[i][j] = 0;
                } else {
                    res[i][j] = res[i - 1][j] + res[i][j - 1];
                }
            }
        }

        return res[row - 1][col - 1];
    }
};