main.cpp

class Solution {
   public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int m = obstacleGrid.size();
        int n = obstacleGrid.front().size();

        vector<int> dp(n, 0);
        for (int j = 0; j < n && obstacleGrid[0][j] == 0; ++j) dp[j] = 1;
        for (int i = 1; i < m; ++i) {
            if (obstacleGrid[i][0] == 1) dp[0] = 0;
            for (int j = 1; j < n; ++j) {
                if (obstacleGrid[i][j] == 1) {
                    dp[j] = 0;
                } else {
                    dp[j] += dp[j - 1];
                }
            }
        }

        return dp.back();
    }
};

class Solution {
   public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int m = obstacleGrid.size();
        int n = obstacleGrid.front().size();

        vector<int> dp(n, 0);
        dp[0] = 1;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (obstacleGrid[i][j] == 1) {
                    dp[j] = 0;
                } else if (j > 0) {
                    dp[j] += dp[j - 1];
                }
            }
        }

        return dp.back();
    }
};