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QOJ

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#641162#8635. 圆hhy0613100 ✓53ms101476kbC++141.0kb2024-10-14 18:56:022024-10-14 18:56:03

Judging History

This is the latest submission verdict.

  • [2024-10-14 18:56:03]
  • Judged
  • Verdict: 100
  • Time: 53ms
  • Memory: 101476kb
  • [2024-10-14 18:56:02]
  • Submitted

answer

#include<bits/stdc++.h>
using namespace std;
const int N=5005,mod=998244353;
int dp[N][N],g[N],fact[N];
int qpow(int a,int b){
	int ans=1;
	while(b>0){
		if(b&1) ans=1ll*ans*a%mod;
		b>>=1;
		a=1ll*a*a%mod;
	} 
	return ans;
}
int main(){
	ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
	int n;
	cin >> n;
	fact[0]=1;
	for(int i=1;i<N;++i) fact[i]=1ll*fact[i-1]*i%mod;
	if(n==3){
		cout << "1\n";
		return 0;
	}
	if(n==4){
		cout << "2\n";
		return 0;
	}
	--n;
	dp[0][0]=1;
	dp[0][1]=1;
	dp[0][2]=1;
	dp[1][1]=1;
	dp[1][2]=2;
	dp[2][2]=1;
	dp[1][3]=3;
	dp[2][3]=3;
	dp[3][3]=1;
	for(int i=1;i<=n;++i){
		for(int j=4;j<=n;++j) dp[i][j]=((dp[i-1][j-1]+dp[i-1][j-2])%mod+dp[i-1][j-3])%mod;
	}
	for(int i=1;i<=n;++i) g[i]=((dp[i-1][n-1]+dp[i-1][n-2])%mod+dp[i-1][n-3])%mod;
	int ans=1;
	for(int x=1;x<=n;++x) ans=(ans+1ll*x*qpow(fact[n],mod-2)%mod*((1ll*g[x]*fact[x]%mod*fact[n-x]%mod+mod-1ll*g[x-1]*fact[x-1]%mod*fact[n-x+1]%mod)%mod)%mod)%mod;
	cout << ans << endl;
	return 0;
}

Details

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Pretests


Final Tests

Test #1:

score: 10
Accepted
time: 0ms
memory: 3688kb

input:

3

output:

1

result:

ok 1 number(s): "1"

Test #2:

score: 10
Accepted
time: 0ms
memory: 5720kb

input:

4

output:

2

result:

ok 1 number(s): "2"

Test #3:

score: 10
Accepted
time: 1ms
memory: 5696kb

input:

6

output:

299473309

result:

ok 1 number(s): "299473309"

Test #4:

score: 10
Accepted
time: 0ms
memory: 3772kb

input:

10

output:

487238321

result:

ok 1 number(s): "487238321"

Test #5:

score: 10
Accepted
time: 1ms
memory: 6132kb

input:

100

output:

41620761

result:

ok 1 number(s): "41620761"

Test #6:

score: 10
Accepted
time: 1ms
memory: 7860kb

input:

200

output:

208771764

result:

ok 1 number(s): "208771764"

Test #7:

score: 10
Accepted
time: 0ms
memory: 14260kb

input:

500

output:

888621375

result:

ok 1 number(s): "888621375"

Test #8:

score: 10
Accepted
time: 47ms
memory: 97480kb

input:

4798

output:

319137015

result:

ok 1 number(s): "319137015"

Test #9:

score: 10
Accepted
time: 52ms
memory: 101476kb

input:

4999

output:

818467659

result:

ok 1 number(s): "818467659"

Test #10:

score: 10
Accepted
time: 53ms
memory: 101472kb

input:

5000

output:

142907477

result:

ok 1 number(s): "142907477"