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IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#621629#8635. 圆larryyu100 ✓15ms202380kbC++20957b2024-10-08 15:47:232024-10-08 15:47:26

Judging History

你现在查看的是最新测评结果

  • [2024-10-08 15:47:26]
  • 评测
  • 测评结果:100
  • 用时:15ms
  • 内存:202380kb
  • [2024-10-08 15:47:23]
  • 提交

answer

#include<bits/stdc++.h>
using namespace std;
#define int long long
const int mo=998244353;
int n;
int dp[5050][5050];
int frac[5050],inv[5050];
int po(int x,int y){
	int z=1;
	while(y){
		if(y%2) z*=x,z%=mo;
		x*=x,x%=mo;
		y/=2;
	}
	return z;
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(nullptr);
	cin>>n;
	if(n==3) cout<<1,exit(0);
	if(n==4) cout<<2,exit(0);
	dp[2][1]=1;
	for(int i=3;i<=n;i++){
		for(int j=1;j<i;j++){
			dp[i][j]=(dp[i-1][j-1]+dp[i-2][j-1]+dp[i-3][j-1])%mo;
		}
	}
	frac[0]=1,inv[0]=1;
	for(int i=1;i<=n;i++){
		frac[i]=frac[i-1]*i%mo;
		inv[i]=po(frac[i],mo-2);
	}
	int ans=0;
	for(int i=1;i<=n;i++){
		ans+=dp[n-2][i]*frac[i]%mo*3%mo*n%mo*frac[n-i-1]%mo*inv[n]%mo*(i+1)%mo;
		ans%=mo;
		ans+=dp[n-3][i]*frac[i]%mo*2%mo*n%mo*frac[n-i-1]%mo*inv[n]%mo*(i+1)%mo;
		ans%=mo;
		ans+=dp[n-4][i]*frac[i]%mo*1%mo*n%mo*frac[n-i-1]%mo*inv[n]%mo*(i+1)%mo;
		ans%=mo;
	}
	cout<<ans;
	return 0;
}

Details

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Pretests


Final Tests

Test #1:

score: 10
Accepted
time: 0ms
memory: 3676kb

input:

3

output:

1

result:

ok 1 number(s): "1"

Test #2:

score: 10
Accepted
time: 0ms
memory: 3568kb

input:

4

output:

2

result:

ok 1 number(s): "2"

Test #3:

score: 10
Accepted
time: 0ms
memory: 3708kb

input:

6

output:

299473309

result:

ok 1 number(s): "299473309"

Test #4:

score: 10
Accepted
time: 0ms
memory: 3712kb

input:

10

output:

487238321

result:

ok 1 number(s): "487238321"

Test #5:

score: 10
Accepted
time: 0ms
memory: 8004kb

input:

100

output:

41620761

result:

ok 1 number(s): "41620761"

Test #6:

score: 10
Accepted
time: 2ms
memory: 11928kb

input:

200

output:

208771764

result:

ok 1 number(s): "208771764"

Test #7:

score: 10
Accepted
time: 0ms
memory: 24196kb

input:

500

output:

888621375

result:

ok 1 number(s): "888621375"

Test #8:

score: 10
Accepted
time: 11ms
memory: 192344kb

input:

4798

output:

319137015

result:

ok 1 number(s): "319137015"

Test #9:

score: 10
Accepted
time: 15ms
memory: 202380kb

input:

4999

output:

818467659

result:

ok 1 number(s): "818467659"

Test #10:

score: 10
Accepted
time: 15ms
memory: 200520kb

input:

5000

output:

142907477

result:

ok 1 number(s): "142907477"