Leetcode #63: Unique Paths II

Leetcode_0063.cpp

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