LeetCode – Refresh – Unique Paths II

We can use a matrix do the dp. Or we can use an array to record it.

But when we encounter 1, we set it to be 0.

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