题解 | #挤奶路径2#

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 cows int整型二维数组 
     * @return int整型
     */
    public int uniquePathsWithCows (int[][] cows) {
        // write code here
        int m = cows.length, n = cows[0].length;
        // 1.找出必经点
        int x = 0, y = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (cows[i][j] == 2) {
                    x = i;
                    y = j;
                }
            }
        }
        // 2.从起点到必经点
        int[][] dp1 = new int[x + 2][y + 2];
        dp1[1][1] = 1;
        for (int i = 1; i < x + 2; i++) {
            for (int j = 1; j < y + 2; j++) {
                if (cows[i - 1][j - 1] != 1 && i * j != 1) {
                    dp1[i][j] = dp1[i - 1][j] + dp1[i][j - 1];
                }
            }
        }
        // 3.从必经点到终点
        int[][] dp2 = new int[m - x + 1][n - y + 1];
        dp2[1][1] = 1;
        for (int i = 1; i < m - x + 1; i++) {
            for (int j = 1; j < n - y + 1; j++) {
                if (cows[i + x - 1][j + y - 1] != 1 && i * j != 1) {
                    dp2[i][j] = dp2[i - 1][j] + dp2[i][j - 1];
                }
            }
        }
        System.out.print(dp2[m - x][n - y]);
        return dp1[x + 1][y + 1] * dp2[m - x][n - y];
    }
}