洛谷P1434 [SHOI2002]滑雪（dfs+记忆化搜索）

关于记忆化搜索：https://blog.csdn.net/hjf1201/article/details/78680814

题目链接：https://www.luogu.org/problem/P1434

思路：将已经搜过的点的结果存起来，当下一次需要搜索这个点时，直接用存储的结果，返回。注意求的是最长路径

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <queue>
#include <vector>
#include <cstring>
#include <map>
#define mem(a) memset(a,0,sizeof(a))
using namespace std;
typedef long long lll;
const int maxn = 200005;
const lll INF = 0x3f3f3f3f3f;
int dir[8][2]= {2,1,1,2,-2,1,-1,2,2,-1,1,-2,-2,-1,-1,-2};
int dir2[4][2]= {0,1,0,-1,1,0,-1,0};
bool flag;
int a[105][105],vis[105][105],ans,r,c;
int dfs(int x, int y){
  //  cout << x <<" "<<y <<" "<< cnt << endl;
   // vis[x][y] = 1;
    if(vis[x][y] != 0) return vis[x][y];
    int t ,tt = 1,i;
    for(i = 0; i < 4; i++)
    {
     int fx = x + dir2[i][0],fy = y + dir2[i][1];
     if(fx > 0 && fx < r+1 && fy > 0 && fy < c+1 && a[fx][fy] < a[x][y])
     {
         t = dfs(fx,fy) + 1;
         tt = max(t,tt);
     }
    }
    vis[x][y] = max(tt,vis[x][y]);
    return vis[x][y];
}
int main()
{

    cin >>r >> c;
    for(int i = 1; i <= r; i++)
    {
        for(int j = 1; j<= c; j++)
            cin >> a[i][j];
    }
    for(int i = 1; i <= r; i++)
    {
        for(int j = 1; j <= c; j++)
        {
            //cout << "==============" << endl;
            //cout << "i = "<< i<<" j = "<< j<< endl;
            vis[i][j] = dfs(i,j);;
            ans = max(ans,vis[i][j]);
           // cout << "==============" << endl;
        }
    }
    cout << ans << endl;
    return 0;
}