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QOJ

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#619181#8635. 圆Augenstern100 ✓97ms241660kbC++141.7kb2024-10-07 13:26:312024-10-07 13:26:31

Judging History

This is the latest submission verdict.

  • [2024-10-07 13:26:31]
  • Judged
  • Verdict: 100
  • Time: 97ms
  • Memory: 241660kb
  • [2024-10-07 13:26:31]
  • Submitted

answer

//#pragma GCC optimize(3)
//#pragma GCC optimize("Ofast,unroll-loops")
#include<bits/stdc++.h>
#define int long long
//#define ull unsigned long long
#define lll __int128
//#define double long double
using namespace std;
const long long INF=1e16+5;
const long long mod=998244353,orm=3;
//const long long mod=1000000007;
const int MAXN=1000005;
const double eps=1e-6;
bool ST;
int n;
int fac[MAXN],inv[MAXN];
int f[5005][5005],g[5005][5005];
int qp(int x,int y) {
	int res=1;
	while(y) {
		if(y&1) y--,res*=x,res%=mod;
		y>>=1,x*=x,x%=mod;
	}
	return res;
}
void add(int &x,int y) {
	x+=y,x%=mod;
}
void solve() {
	cin>>n;
	fac[0]=inv[0]=1;
	for(int i=1;i<=n;i++) fac[i]=fac[i-1]*i%mod;
	for(int i=1;i<=n;i++) inv[i]=inv[i-1]*qp(n-i+1,mod-2)%mod;
	f[0][0]=1;
	for(int i=1;i<=n-4;i++) {
		for(int j=1;j<=i;j++) {
			add(f[i][j],f[i-1][j-1]);
			if(i>=2) add(f[i][j],f[i-2][j-1]);
			if(i>=3) add(f[i][j],f[i-3][j-1]);
		}
	}
	g[1][1]=1,g[2][1]=1,g[2][2]=1;
	for(int i=3;i<=n-3;i++) {
		for(int j=1;j<=i;j++) {
			add(g[i][j],g[i-1][j-1]);
			if(i>=2) add(g[i][j],g[i-2][j-1]);
			if(i>=3) add(g[i][j],g[i-3][j-1]);
		}
	}
	int res=0;
	for(int i=0;i<=n-3;i++) {
		int val=g[n-3][i];
		if(n>=4) val+=g[n-4][i],val%=mod;
		if(n==3) val=1;
		res+=fac[i]*val%mod*(i+1)%mod*inv[i+1]%mod,res%=mod;
	}
	if(n>=4) {
		for(int i=0;i<=n-4;i++) {
			res+=fac[i+1]*f[n-4][i]%mod*(i+2)%mod*inv[i+2]%mod*2,res%=mod;
		}
	}
	res*=n,res%=mod;
	cout<<res;
}
bool ED;
signed main() {
//	cout<<(&ST-&ED)/1024.0/1024.0;
//	freopen("color.in","r",stdin);
//	freopen("color.out","w",stdout);
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	solve();
	return 0;
}

Details

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Pretests


Final Tests

Test #1:

score: 10
Accepted
time: 1ms
memory: 9856kb

input:

3

output:

1

result:

ok 1 number(s): "1"

Test #2:

score: 10
Accepted
time: 1ms
memory: 9856kb

input:

4

output:

2

result:

ok 1 number(s): "2"

Test #3:

score: 10
Accepted
time: 1ms
memory: 9748kb

input:

6

output:

299473309

result:

ok 1 number(s): "299473309"

Test #4:

score: 10
Accepted
time: 0ms
memory: 9756kb

input:

10

output:

487238321

result:

ok 1 number(s): "487238321"

Test #5:

score: 10
Accepted
time: 0ms
memory: 10480kb

input:

100

output:

41620761

result:

ok 1 number(s): "41620761"

Test #6:

score: 10
Accepted
time: 2ms
memory: 11516kb

input:

200

output:

208771764

result:

ok 1 number(s): "208771764"

Test #7:

score: 10
Accepted
time: 0ms
memory: 15584kb

input:

500

output:

888621375

result:

ok 1 number(s): "888621375"

Test #8:

score: 10
Accepted
time: 67ms
memory: 227048kb

input:

4798

output:

319137015

result:

ok 1 number(s): "319137015"

Test #9:

score: 10
Accepted
time: 97ms
memory: 241660kb

input:

4999

output:

818467659

result:

ok 1 number(s): "818467659"

Test #10:

score: 10
Accepted
time: 87ms
memory: 241272kb

input:

5000

output:

142907477

result:

ok 1 number(s): "142907477"