63. 不同路径 II

https://leetcode.cn/problems/unique-paths-ii/

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int m = obstacleGrid.size();
        int n = 0;
        if (m > 0) {
            n = obstacleGrid[0].size();
        }
         // 二维dp数组
        vector<vector<int> >dp(m, vector<int>(n, 0));
        //初始化
        for (int j = 0; j<n; j++) {
            if (obstacleGrid[0][j] != 1) {
                dp[0][j] = 1;
            }
        }
        for (int i = 0; i< m; i++) {
            if (obstacleGrid[i][0] != 1) {
                dp[i][0] = 1;
            }
        }

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

        return dp[m-1][n-1];
    }
};