题解 | 不同路径的数目(二)

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param obstacleGrid char字符型ArrayList<ArrayList<>>
     * @return int整型
     */
    public int uniquePathsWithObstacles (ArrayList<ArrayList<Character>>
                                         obstacleGrid) {
        // write code here
        int m = obstacleGrid.size();
        int n = obstacleGrid.get(0).size();
        int[][] dp = new int[m + 1][n + 1];
        if(obstacleGrid.get(0).get(0)=='#') return 0;
        dp[0][0] = 1;
        for (int i = 1; i < m; i++) {
            if (obstacleGrid.get(i).get(0) == 'A') dp[i][0] = dp[i - 1][0];
            else dp[i][0] = 0;
        }

        for (int j = 1; j < n; j++) {
            if (obstacleGrid.get(0).get(j) == 'A') dp[0][j] = dp[0][j-1];
            else dp[0][j] = 0;
        }

        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++) {
                if(obstacleGrid.get(i).get(j)=='A')
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                else
                    dp[i][j] = 0;
            }
        }
        return dp[m - 1][n - 1];
    }
}