View Code of Problem 217

import java.util.Scanner;

public class main {
    //四个方向
    static int p[][] = { {1, 0}, {0, 1},{-1, 0}, {0, -1}};
    static int max = Integer.MIN_VALUE, r, c;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        r = sc.nextInt();
        c = sc.nextInt();
        int[][] a = new int[r][c];
        for (int i = 0; i < r; i++) {
            for (int j = 0; j < c; j++) {
                a[i][j] = sc.nextInt();
            }
        }
        for (int i = 0; i < r; i++)
        {
            for (int j = 0; j < c; j++)
            {
                dfs(a, i, j, 1);
            }
        }
        System.out.println(max);
    }

    public static void dfs(int[][] a, int i, int j, int sum) {
        int t, x, y;
        if (sum > max)//找出可以走的路径中的最大值
            max = sum;
        for (t = 0; t < 4; t++)//向上下左右分别搜索
        {
            x = i + p[t][0];//在节点处向上和下移动
            y = j + p[t][1];//在节点处向左和右移动
            if (x >= 0 && x < r && y >= 0 && y < c && a[x][y] < a[i][j])//如果没有超出数组边界且这个节点比原来的小
            {
                sum++;//我们的路的长度加一
                dfs(a, x, y, sum);//在新节点重复此次循环，到达路径最小处结束循环
                sum--;//回溯到可以走的节点时把走过的路的长度减去
            }
        }

    }
}


/*
F:\temp\21425366.618876\Main.java:6: class main is public, should be declared in a file named main.java
public class main {
       ^
1 error
*/