OpenJ_Bailian - 1088

题解：DFS记忆化搜索

记忆化搜索也可以说是动态规划，最后的答案也是从一个个子问题推导而来

#include <bits/stdc++.h>
#define Zeoy std::ios::sync_with_stdio(false), std::cin.tie(0), std::cout.tie(0)
#define all(x) (x).begin(), (x).end()
#define endl '\n'
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-9;
const int N = 2e5 + 10;
int n, m;
int g[110][110];
int dis[110][110]; // dis[x][y]代表从坐标(x,y)的点出发的最长路径
int vis[110][110];
int dir[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
int dfs(int sx, int sy)
{
    if (dis[sx][sy])
        return dis[sx][sy];
    dis[sx][sy] = 1;
    for (int i = 0; i < 4; ++i)
    {
        int nx = sx + dir[i][0];
        int ny = sy + dir[i][1];
        if (nx >= 1 && nx <= n && ny >= 1 && ny <= m && !vis[nx][ny] && g[nx][ny] < g[sx][sy])
        {
            vis[nx][ny] = 1;
            dis[sx][sy] = max(dfs(nx, ny) + 1, dis[sx][sy]);
            vis[nx][ny] = 0;
        }
    }
    return dis[sx][sy];
}
int main(void)
{
    Zeoy;
    int t = 1;
    while (t--)
    {
        cin >> n >> m;
        for (int i = 1; i <= n; ++i)
            for (int j = 1; j <= m; ++j)
                cin >> g[i][j];
        int ans = -inf;
        for (int i = 1; i <= n; ++i)
        {
            for (int j = 1; j <= m; ++j)
            {
                ans = max(dfs(i, j), ans);
            }
        }
        cout << ans << endl;
    }
    return 0;
}