原题链接：https://leetcode.com/problems/unique-paths-ii/

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