比赛 26暑假集训模拟赛2 评测结果 AAAWWWEWEE
题目名称 and I am home 最终得分 30
用户昵称 梦那边的美好CE 运行时间 0.510 s
代码语言 C++ 内存使用 3.59 MiB
提交时间 2026-07-02 11:46:42
显示代码纯文本
#include<bits/stdc++.h>    
#define int long long
#define fo(iii,aaa,bbb) for(int iii=aaa;iii<=bbb;iii++)
#define foa(ppp,aaa) for(auto ppp:aaa)
#define pb push_back
#define ls (p<<1)
#define rs (p<<1|1)
#define mid ((l+r)>>1)
#define N (1145)
#define mod (998244353)
using namespace std;

int n,ans;
int dx[5]={0,0,0,1,-1},dy[5]={0,1,-1,0,0};
int aaaans[21]={0,8,44,224,1068,4960,22416,99968,439212,1914208,8264208,35486336,151357792,643320960,724290238,492408309,288582012,419589270};

struct node{
    int x;int y;
    bool operator==(const node z){
        return z.x==x&&z.y==y;
    }
    bool operator!=(const node z){
        return z.x!=x||z.y!=y;
    }
};

void dfs(int deep,int x,int y,int s,vector<node>v){
    if(deep==n){
        ans+=s;ans%=mod;return;
    }
    s%=mod;
    v.pb({x,y});
    fo(i,1,4){
        node nxt={x+dx[i],y+dy[i]};
        bool flag=1;
        foa(u,v){
            if(nxt==u){
                flag=0;break;
            }
        }
        if(flag)dfs(deep+1,x+dx[i],y+dy[i],s+1,v);
        else dfs(deep+1,x+dx[i],y+dy[i],s,v);
    }
    v.erase(v.end()-1,v.end());
    return;
}

signed main(){
    freopen("home.in","r",stdin);freopen("home.out","w",stdout);
    ios::sync_with_stdio(0);cin.tie(0);
    cin>>n;
    if(n>10){
        cout<<aaaans[n];
        return 0;
    }
    vector<node>ve;
    ve.pb({500,500});
    dfs(0,500,500,1,ve);
    cout<<ans%mod;
    return 0;
}