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ID题目提交者结果用时内存语言文件大小提交时间测评时间
#80202#5406. 随机游走tricyzhkx100 ✓778ms418472kbC++141.3kb2023-02-23 08:35:272023-02-23 08:35:31

Judging History

你现在查看的是最新测评结果

  • [2023-08-10 23:21:45]
  • System Update: QOJ starts to keep a history of the judgings of all the submissions.
  • [2023-02-23 08:35:31]
  • 评测
  • 测评结果:100
  • 用时:778ms
  • 内存:418472kb
  • [2023-02-23 08:35:27]
  • 提交

answer

# include <bits/stdc++.h>
using namespace std;
const int mod=1e9+7,_2=(mod+1)/2;
typedef long long ll;
int n,prime[2000010],tot;
bool nopri[20000010];
ll pw[20000010],fac[10000010],inv[10000010],finv[10000010];
ll C(int n,int m){return fac[n]*finv[n-m]%mod*finv[m]%mod;}
ll power(ll a,int b)
{
	ll ans=1;
	for(;b;b>>=1,a=a*a%mod)
		if(b&1) ans=ans*a%mod;
	return ans;
}
ll calc(int m,int a)// \int_0^m x^{2*n-1}(x-a) dx
{
	return (m*inv[2*n+1]+(mod-a)*inv[2*n])%mod*pw[m]%mod;
}
int main()
{
	int ans=0;
	cin>>n;
	fac[0]=fac[1]=inv[0]=inv[1]=finv[0]=finv[1]=1;
	for(int i=2;i<=2*n+1;i++) fac[i]=fac[i-1]*i%mod;
	for(int i=2;i<=2*n+1;i++) inv[i]=(mod-mod/i)*inv[mod%i]%mod;
	for(int i=2;i<=2*n+1;i++) finv[i]=finv[i-1]*inv[i]%mod;
	nopri[0]=nopri[1]=1;pw[1]=1;
	for(int i=2;i<=4*n;i++)
	{
		if(!nopri[i]) prime[++tot]=i,pw[i]=power(i,2*n);
		for(int j=1;j<=tot && i*prime[j]<=4*n;j++)
		{
			nopri[i*prime[j]]=1;
			pw[i*prime[j]]=pw[i]*pw[prime[j]]%mod;
			if(i%prime[j]==0) break;
		}
	}
	ll w=finv[2*n-1]*power(_2,2*n)%mod;
	for(int i=0;i<=2*n;i++)
	{
		ll w1=(i&1?mod-C(2*n,i):C(2*n,i))*w%mod;
		if(i<=n) ans=(ans+w1*(mod-calc(2*n-2*i,2*n-2*i)))%mod;
		ans=(ans+w1*(calc(4*n-2*i,2*n-2*i)-calc(max(0,2*n-2*i),2*n-2*i)+mod))%mod;
	}
	cout<<(ll)ans*_2%mod<<endl;
	return 0;
}

详细

Subtask #1:

score: 5
Accepted

Test #1:

score: 5
Accepted
time: 0ms
memory: 3340kb

input:

1

output:

333333336

result:

ok 1 number(s): "333333336"

Test #2:

score: 0
Accepted
time: 2ms
memory: 3372kb

input:

2

output:

266666669

result:

ok 1 number(s): "266666669"

Test #3:

score: 0
Accepted
time: 1ms
memory: 3276kb

input:

3

output:

769047625

result:

ok 1 number(s): "769047625"

Subtask #2:

score: 10
Accepted

Test #4:

score: 10
Accepted
time: 0ms
memory: 3400kb

input:

4

output:

877865968

result:

ok 1 number(s): "877865968"

Test #5:

score: 0
Accepted
time: 0ms
memory: 3292kb

input:

5

output:

733342859

result:

ok 1 number(s): "733342859"

Test #6:

score: 0
Accepted
time: 2ms
memory: 3368kb

input:

6

output:

655899114

result:

ok 1 number(s): "655899114"

Test #7:

score: 0
Accepted
time: 2ms
memory: 3524kb

input:

7

output:

946326757

result:

ok 1 number(s): "946326757"

Test #8:

score: 0
Accepted
time: 2ms
memory: 3368kb

input:

8

output:

230714822

result:

ok 1 number(s): "230714822"

Test #9:

score: 0
Accepted
time: 1ms
memory: 3328kb

input:

9

output:

782967541

result:

ok 1 number(s): "782967541"

Test #10:

score: 0
Accepted
time: 2ms
memory: 3372kb

input:

10

output:

732371611

result:

ok 1 number(s): "732371611"

Subtask #3:

score: 10
Accepted

Test #11:

score: 10
Accepted
time: 2ms
memory: 3356kb

input:

15

output:

677123472

result:

ok 1 number(s): "677123472"

Test #12:

score: 0
Accepted
time: 0ms
memory: 3352kb

input:

13

output:

168974634

result:

ok 1 number(s): "168974634"

Test #13:

score: 0
Accepted
time: 0ms
memory: 3400kb

input:

26

output:

213343876

result:

ok 1 number(s): "213343876"

Test #14:

score: 0
Accepted
time: 2ms
memory: 3380kb

input:

29

output:

631124616

result:

ok 1 number(s): "631124616"

Subtask #4:

score: 15
Accepted

Test #15:

score: 15
Accepted
time: 2ms
memory: 3328kb

input:

37

output:

349256161

result:

ok 1 number(s): "349256161"

Test #16:

score: 0
Accepted
time: 0ms
memory: 3404kb

input:

104

output:

351095881

result:

ok 1 number(s): "351095881"

Test #17:

score: 0
Accepted
time: 2ms
memory: 3392kb

input:

194

output:

895504391

result:

ok 1 number(s): "895504391"

Test #18:

score: 0
Accepted
time: 2ms
memory: 3380kb

input:

197

output:

923555376

result:

ok 1 number(s): "923555376"

Test #19:

score: 0
Accepted
time: 2ms
memory: 3380kb

input:

198

output:

512220517

result:

ok 1 number(s): "512220517"

Subtask #5:

score: 15
Accepted

Test #20:

score: 15
Accepted
time: 1ms
memory: 3460kb

input:

562

output:

255062346

result:

ok 1 number(s): "255062346"

Test #21:

score: 0
Accepted
time: 1ms
memory: 3408kb

input:

1007

output:

735041605

result:

ok 1 number(s): "735041605"

Test #22:

score: 0
Accepted
time: 2ms
memory: 3420kb

input:

1788

output:

208261384

result:

ok 1 number(s): "208261384"

Test #23:

score: 0
Accepted
time: 2ms
memory: 3516kb

input:

1980

output:

875427987

result:

ok 1 number(s): "875427987"

Test #24:

score: 0
Accepted
time: 0ms
memory: 3580kb

input:

1983

output:

571776252

result:

ok 1 number(s): "571776252"

Test #25:

score: 0
Accepted
time: 2ms
memory: 3440kb

input:

1992

output:

12983695

result:

ok 1 number(s): "12983695"

Subtask #6:

score: 15
Accepted

Test #26:

score: 15
Accepted
time: 2ms
memory: 3744kb

input:

3946

output:

977435333

result:

ok 1 number(s): "977435333"

Test #27:

score: 0
Accepted
time: 8ms
memory: 8848kb

input:

65944

output:

312666196

result:

ok 1 number(s): "312666196"

Test #28:

score: 0
Accepted
time: 24ms
memory: 16972kb

input:

163815

output:

163767254

result:

ok 1 number(s): "163767254"

Test #29:

score: 0
Accepted
time: 20ms
memory: 20092kb

input:

198732

output:

911833524

result:

ok 1 number(s): "911833524"

Test #30:

score: 0
Accepted
time: 28ms
memory: 20012kb

input:

199287

output:

910277128

result:

ok 1 number(s): "910277128"

Test #31:

score: 0
Accepted
time: 22ms
memory: 19908kb

input:

199819

output:

561747634

result:

ok 1 number(s): "561747634"

Subtask #7:

score: 30
Accepted

Test #32:

score: 30
Accepted
time: 35ms
memory: 29688kb

input:

315618

output:

602805814

result:

ok 1 number(s): "602805814"

Test #33:

score: 0
Accepted
time: 149ms
memory: 97324kb

input:

1130465

output:

898203793

result:

ok 1 number(s): "898203793"

Test #34:

score: 0
Accepted
time: 691ms
memory: 368696kb

input:

4399723

output:

101317224

result:

ok 1 number(s): "101317224"

Test #35:

score: 0
Accepted
time: 728ms
memory: 403404kb

input:

4804460

output:

114947085

result:

ok 1 number(s): "114947085"

Test #36:

score: 0
Accepted
time: 748ms
memory: 418176kb

input:

4995726

output:

460040939

result:

ok 1 number(s): "460040939"

Test #37:

score: 0
Accepted
time: 741ms
memory: 418472kb

input:

4999919

output:

780785591

result:

ok 1 number(s): "780785591"

Test #38:

score: 0
Accepted
time: 778ms
memory: 418472kb

input:

4999999

output:

742624725

result:

ok 1 number(s): "742624725"