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QOJ
| 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 |
|---|---|---|---|---|---|---|---|---|---|
| #110071 | #5406. 随机游走 | vme50 | 100 ✓ | 377ms | 136788kb | C++17 | 1.1kb | 2023-05-31 14:32:58 | 2023-05-31 14:32:59 |
Judging History
answer
#include <bits/stdc++.h>
using namespace std;
#define N 10000005
#define MOD 1000000007
int n,invN,invN1,pw2,ans,fc[N],invFc[N],p[N],pw[N];bool vs[N];
void W(int &x,int y) {x+=y;if(x>=MOD) x-=MOD;}
int qPow(int x,int y)
{
int res=1;
for(;y;y/=2,x=1ll*x*x%MOD) if(y&1)
res=1ll*res*x%MOD;return res;
}
void init(int n)
{
fc[0]=invFc[0]=1;for(int i=1;i<=n;++i) fc[i]=1ll*fc[i-1]*i%MOD;
invFc[n]=qPow(fc[n],MOD-2);
for(int i=n-1;i;--i) invFc[i]=1ll*invFc[i+1]*(i+1)%MOD;
}
void sieve(int n)
{
vs[1]=pw[1]=1;
for(int i=2;i<=n;++i)
{
if(!vs[i]) p[++p[0]]=i,pw[i]=qPow(i,n);
for(int j=1;i*p[j]<=n;++j)
{
vs[i*p[j]]=1;pw[i*p[j]]=1ll*pw[i]*pw[p[j]]%MOD;
if(!(i%p[j])) break;
}
}
}
int main()
{
scanf("%d",&n);n*=2;init(n);sieve(n);
invN=qPow(n,MOD-2);invN1=qPow(n+1,MOD-2);pw2=qPow(2,n);
for(int i=0,t;i<=n;++i)
{
t=(2ll*(n-i)*invN1-1ll*(n-i*2)*invN)%MOD*pw[n-i]%MOD*pw2%MOD;
if(i*2<n) t=(t+1ll*(invN-invN1)*(n-i*2)%MOD*pw[n-i*2])%MOD;
t=1ll*(t+MOD)*invFc[i]%MOD*invFc[n-i]%MOD;W(ans,i&1?MOD-t:t);
}ans=1ll*ans*qPow(pw2,MOD-2)%MOD*n%MOD;printf("%d\n",ans);return 0;
}
详细
Subtask #1:
score: 5
Accepted
Test #1:
score: 5
Accepted
time: 0ms
memory: 9932kb
input:
1
output:
333333336
result:
ok 1 number(s): "333333336"
Test #2:
score: 0
Accepted
time: 0ms
memory: 11788kb
input:
2
output:
266666669
result:
ok 1 number(s): "266666669"
Test #3:
score: 0
Accepted
time: 1ms
memory: 9748kb
input:
3
output:
769047625
result:
ok 1 number(s): "769047625"
Subtask #2:
score: 10
Accepted
Test #4:
score: 10
Accepted
time: 0ms
memory: 9680kb
input:
4
output:
877865968
result:
ok 1 number(s): "877865968"
Test #5:
score: 0
Accepted
time: 1ms
memory: 9920kb
input:
5
output:
733342859
result:
ok 1 number(s): "733342859"
Test #6:
score: 0
Accepted
time: 2ms
memory: 9708kb
input:
6
output:
655899114
result:
ok 1 number(s): "655899114"
Test #7:
score: 0
Accepted
time: 2ms
memory: 9756kb
input:
7
output:
946326757
result:
ok 1 number(s): "946326757"
Test #8:
score: 0
Accepted
time: 4ms
memory: 9744kb
input:
8
output:
230714822
result:
ok 1 number(s): "230714822"
Test #9:
score: 0
Accepted
time: 0ms
memory: 9924kb
input:
9
output:
782967541
result:
ok 1 number(s): "782967541"
Test #10:
score: 0
Accepted
time: 2ms
memory: 9852kb
input:
10
output:
732371611
result:
ok 1 number(s): "732371611"
Subtask #3:
score: 10
Accepted
Test #11:
score: 10
Accepted
time: 4ms
memory: 9684kb
input:
15
output:
677123472
result:
ok 1 number(s): "677123472"
Test #12:
score: 0
Accepted
time: 2ms
memory: 9688kb
input:
13
output:
168974634
result:
ok 1 number(s): "168974634"
Test #13:
score: 0
Accepted
time: 3ms
memory: 9860kb
input:
26
output:
213343876
result:
ok 1 number(s): "213343876"
Test #14:
score: 0
Accepted
time: 4ms
memory: 9740kb
input:
29
output:
631124616
result:
ok 1 number(s): "631124616"
Subtask #4:
score: 15
Accepted
Test #15:
score: 15
Accepted
time: 5ms
memory: 9748kb
input:
37
output:
349256161
result:
ok 1 number(s): "349256161"
Test #16:
score: 0
Accepted
time: 0ms
memory: 9904kb
input:
104
output:
351095881
result:
ok 1 number(s): "351095881"
Test #17:
score: 0
Accepted
time: 3ms
memory: 9756kb
input:
194
output:
895504391
result:
ok 1 number(s): "895504391"
Test #18:
score: 0
Accepted
time: 6ms
memory: 9744kb
input:
197
output:
923555376
result:
ok 1 number(s): "923555376"
Test #19:
score: 0
Accepted
time: 2ms
memory: 9772kb
input:
198
output:
512220517
result:
ok 1 number(s): "512220517"
Subtask #5:
score: 15
Accepted
Test #20:
score: 15
Accepted
time: 2ms
memory: 9740kb
input:
562
output:
255062346
result:
ok 1 number(s): "255062346"
Test #21:
score: 0
Accepted
time: 2ms
memory: 9904kb
input:
1007
output:
735041605
result:
ok 1 number(s): "735041605"
Test #22:
score: 0
Accepted
time: 2ms
memory: 9932kb
input:
1788
output:
208261384
result:
ok 1 number(s): "208261384"
Test #23:
score: 0
Accepted
time: 1ms
memory: 9692kb
input:
1980
output:
875427987
result:
ok 1 number(s): "875427987"
Test #24:
score: 0
Accepted
time: 0ms
memory: 9668kb
input:
1983
output:
571776252
result:
ok 1 number(s): "571776252"
Test #25:
score: 0
Accepted
time: 4ms
memory: 9744kb
input:
1992
output:
12983695
result:
ok 1 number(s): "12983695"
Subtask #6:
score: 15
Accepted
Test #26:
score: 15
Accepted
time: 4ms
memory: 9720kb
input:
3946
output:
977435333
result:
ok 1 number(s): "977435333"
Test #27:
score: 0
Accepted
time: 4ms
memory: 10036kb
input:
65944
output:
312666196
result:
ok 1 number(s): "312666196"
Test #28:
score: 0
Accepted
time: 16ms
memory: 16320kb
input:
163815
output:
163767254
result:
ok 1 number(s): "163767254"
Test #29:
score: 0
Accepted
time: 15ms
memory: 20232kb
input:
198732
output:
911833524
result:
ok 1 number(s): "911833524"
Test #30:
score: 0
Accepted
time: 18ms
memory: 14372kb
input:
199287
output:
910277128
result:
ok 1 number(s): "910277128"
Test #31:
score: 0
Accepted
time: 15ms
memory: 14368kb
input:
199819
output:
561747634
result:
ok 1 number(s): "561747634"
Subtask #7:
score: 30
Accepted
Test #32:
score: 30
Accepted
time: 19ms
memory: 16656kb
input:
315618
output:
602805814
result:
ok 1 number(s): "602805814"
Test #33:
score: 0
Accepted
time: 80ms
memory: 37764kb
input:
1130465
output:
898203793
result:
ok 1 number(s): "898203793"
Test #34:
score: 0
Accepted
time: 336ms
memory: 121804kb
input:
4399723
output:
101317224
result:
ok 1 number(s): "101317224"
Test #35:
score: 0
Accepted
time: 355ms
memory: 132240kb
input:
4804460
output:
114947085
result:
ok 1 number(s): "114947085"
Test #36:
score: 0
Accepted
time: 376ms
memory: 134740kb
input:
4995726
output:
460040939
result:
ok 1 number(s): "460040939"
Test #37:
score: 0
Accepted
time: 377ms
memory: 134732kb
input:
4999919
output:
780785591
result:
ok 1 number(s): "780785591"
Test #38:
score: 0
Accepted
time: 377ms
memory: 136788kb
input:
4999999
output:
742624725
result:
ok 1 number(s): "742624725"