[SHOI2002]滑雪 （记忆化搜索模版）

#include <algorithm>
#include <string>
#include <string.h>
#include <vector>
#include <map>
#include <stack>
#include <set>
#include <queue>
#include <math.h>
#include <cstdio>
#include <iomanip>
#include <time.h>
#include <bitset>
#include <cmath>
#include <sstream>
#include <iostream>
#include <cstring>

#define LL long long
#define ls nod<<1
#define rs (nod<<1)+1
#define pii pair<int,int>
#define mp make_pair
#define pb push_back

const double eps = 1e-10;
const int maxn = 100 + 10;
const LL mod = 1e9 + 7;
const LL INF = 1e18;

int sgn(double a){return a < -eps ? -1 : a < eps ? 0 : 1;}
using namespace std;

int mapp[maxn][maxn];
int f[maxn][maxn];
int n,m;
int dir[4][2] = {{-1,0},{1,0},{0,-1},{0,1}};

inline int dfs(int x,int y,int last) {
    if (f[x][y])
        return f[x][y];
    f[x][y] = 1;
    for (int i = 0;i < 4;i++) {
        int xx = x + dir[i][0];
        int yy = y + dir[i][1];
        if (mapp[xx][yy] < last && xx >= 1 && xx <= n && yy >= 1 && yy <= n) {
            dfs(xx,yy,mapp[xx][yy]);
            f[x][y] = max(f[x][y],f[xx][yy]+1);
        }
    }
    return f[x][y];
}


int main() {
    cin >> n >> m;
    for (int i = 1;i <= n;i++) {
        for (int j = 1;j <= m;j++)
            cin >> mapp[i][j];
    }
    int ans = 0;
    for (int i = 1;i <= n;i++) {
        for (int j = 1;j <= m;j++) {
            ans = max(ans,dfs(i,j,mapp[i][j]));
        }
    }
    cout << ans << endl;
    return 0;
}