QOJ.ac
QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#591650 | #8635. 圆 | jianhe | 40 | 2ms | 3728kb | C++14 | 1.1kb | 2024-09-26 17:01:53 | 2024-09-26 17:01:53 |
Judging History
answer
#include<bits/stdc++.h>
using namespace std;
#define ll long long
const ll mod=998244353,N=5050;
ll n,ans,ct,jc[N],col[N];
bool vis[N];
ll ksm(ll a,ll b){
ll ct=1;
while(b){
if(b&1) ct=ct*a%mod;
b>>=1,a=a*a%mod;
}
return ct;
}
//void init(){jc[0]=1;for(int i=1;i<=n;i++) jc[i]=jc[i-1]*i%mod;}
//ll A(ll n,ll m){return jc[n]*ksm(jc[n-m],mod-2)%mod;}
ll lt(ll i){if(i==1) return n;return i-1;}
ll nt(ll i){if(i==n) return 1;return i+1;}
ll dfs(ll s){
if(s>=n) return 0;
ll res=0,ct=0;
for(int i=1;i<=n;i++)
if(vis[i]==0){
ll t=(col[i]==0)+(col[lt(i)]==0)+(col[nt(i)]==0);
vis[i]=1,col[lt(i)]++,col[nt(i)]++,col[i]++;
res+=dfs(s+t)+1,ct++;
vis[i]=0;col[lt(i)]--,col[nt(i)]--,col[i]--;
}
return res*ksm(ct,mod-2)%mod;
}
int main(){
ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
cin>>n;//init();
// for(int x=2;x<=n-2;x++) ans+=(A(n-1,x-1)-A(n-2,x-2)*(x-1))%mod*x%mod,ct+=(A(n-1,x-1)-A(n-2,x-2)*(x-1))%mod,cout<<ct<<"\n";
// ans%=mod,ct%=mod;
// ans=ans*ksm(ct,mod-2)%mod;
// cout<<ans;
vis[1]=1;col[1]=col[2]=col[n]=1;
cout<<(dfs(3)+1)%mod;
return 0;
}
Details
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Pretests
Final Tests
Test #1:
score: 10
Accepted
time: 0ms
memory: 3660kb
input:
3
output:
1
result:
ok 1 number(s): "1"
Test #2:
score: 10
Accepted
time: 0ms
memory: 3540kb
input:
4
output:
2
result:
ok 1 number(s): "2"
Test #3:
score: 10
Accepted
time: 0ms
memory: 3660kb
input:
6
output:
299473309
result:
ok 1 number(s): "299473309"
Test #4:
score: 10
Accepted
time: 2ms
memory: 3728kb
input:
10
output:
487238321
result:
ok 1 number(s): "487238321"
Test #5:
score: 0
Time Limit Exceeded
input:
100
output:
result:
Test #6:
score: 0
Time Limit Exceeded
input:
200
output:
result:
Test #7:
score: 0
Time Limit Exceeded
input:
500
output:
result:
Test #8:
score: 0
Time Limit Exceeded
input:
4798
output:
result:
Test #9:
score: 0
Time Limit Exceeded
input:
4999
output:
result:
Test #10:
score: 0
Time Limit Exceeded
input:
5000