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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 |
|---|---|---|---|---|---|---|---|---|---|
| #396077 | #5406. 随机游走 | linweitong | 100 ✓ | 545ms | 85876kb | C++20 | 668b | 2024-04-22 11:45:49 | 2024-04-22 11:45:51 |
Judging History
answer
#include<bits/stdc++.h>
using namespace std;
const int N=20000005,mod=1e9+7;
int n,fac[N],ifac[N];
int ksm(int x,int y){
int s=1;
while (y){
if (y&1)s=1ll*s*x%mod;
x=1ll*x*x%mod,y>>=1;
}
return s;
}
int main(){
cin>>n;int m=2*n;
fac[0]=1;
for (int i=1;i<=2*n;++i)fac[i]=1ll*fac[i-1]*i%mod;
ifac[2*n]=ksm(fac[2*n],mod-2);
for (int i=2*n-1;i>=0;--i)ifac[i]=1ll*ifac[i+1]*(i+1)%mod;
int anss=0,inv=ksm(m+1,mod-2);
for (int i=0;i<n;++i){
if (i&1)anss=(anss+mod-1ll*ifac[i]*ifac[m-i]%mod*ksm(n-i,m+1)%mod*inv%mod)%mod;
else anss=(anss+1ll*ifac[i]*ifac[m-i]%mod*ksm(n-i,m+1)%mod*inv%mod)%mod;
}
anss*=2,anss%=mod;
cout<<anss;
}
详细
Subtask #1:
score: 5
Accepted
Test #1:
score: 5
Accepted
time: 1ms
memory: 5700kb
input:
1
output:
333333336
result:
ok 1 number(s): "333333336"
Test #2:
score: 0
Accepted
time: 1ms
memory: 5704kb
input:
2
output:
266666669
result:
ok 1 number(s): "266666669"
Test #3:
score: 0
Accepted
time: 1ms
memory: 5760kb
input:
3
output:
769047625
result:
ok 1 number(s): "769047625"
Subtask #2:
score: 10
Accepted
Test #4:
score: 10
Accepted
time: 1ms
memory: 5788kb
input:
4
output:
877865968
result:
ok 1 number(s): "877865968"
Test #5:
score: 0
Accepted
time: 0ms
memory: 5640kb
input:
5
output:
733342859
result:
ok 1 number(s): "733342859"
Test #6:
score: 0
Accepted
time: 0ms
memory: 5788kb
input:
6
output:
655899114
result:
ok 1 number(s): "655899114"
Test #7:
score: 0
Accepted
time: 1ms
memory: 5704kb
input:
7
output:
946326757
result:
ok 1 number(s): "946326757"
Test #8:
score: 0
Accepted
time: 0ms
memory: 5584kb
input:
8
output:
230714822
result:
ok 1 number(s): "230714822"
Test #9:
score: 0
Accepted
time: 0ms
memory: 5636kb
input:
9
output:
782967541
result:
ok 1 number(s): "782967541"
Test #10:
score: 0
Accepted
time: 0ms
memory: 5788kb
input:
10
output:
732371611
result:
ok 1 number(s): "732371611"
Subtask #3:
score: 10
Accepted
Test #11:
score: 10
Accepted
time: 0ms
memory: 5704kb
input:
15
output:
677123472
result:
ok 1 number(s): "677123472"
Test #12:
score: 0
Accepted
time: 0ms
memory: 5580kb
input:
13
output:
168974634
result:
ok 1 number(s): "168974634"
Test #13:
score: 0
Accepted
time: 0ms
memory: 5712kb
input:
26
output:
213343876
result:
ok 1 number(s): "213343876"
Test #14:
score: 0
Accepted
time: 0ms
memory: 5576kb
input:
29
output:
631124616
result:
ok 1 number(s): "631124616"
Subtask #4:
score: 15
Accepted
Test #15:
score: 15
Accepted
time: 0ms
memory: 5700kb
input:
37
output:
349256161
result:
ok 1 number(s): "349256161"
Test #16:
score: 0
Accepted
time: 1ms
memory: 5708kb
input:
104
output:
351095881
result:
ok 1 number(s): "351095881"
Test #17:
score: 0
Accepted
time: 1ms
memory: 5700kb
input:
194
output:
895504391
result:
ok 1 number(s): "895504391"
Test #18:
score: 0
Accepted
time: 1ms
memory: 5580kb
input:
197
output:
923555376
result:
ok 1 number(s): "923555376"
Test #19:
score: 0
Accepted
time: 1ms
memory: 5704kb
input:
198
output:
512220517
result:
ok 1 number(s): "512220517"
Subtask #5:
score: 15
Accepted
Test #20:
score: 15
Accepted
time: 1ms
memory: 5704kb
input:
562
output:
255062346
result:
ok 1 number(s): "255062346"
Test #21:
score: 0
Accepted
time: 1ms
memory: 5640kb
input:
1007
output:
735041605
result:
ok 1 number(s): "735041605"
Test #22:
score: 0
Accepted
time: 1ms
memory: 5780kb
input:
1788
output:
208261384
result:
ok 1 number(s): "208261384"
Test #23:
score: 0
Accepted
time: 0ms
memory: 5652kb
input:
1980
output:
875427987
result:
ok 1 number(s): "875427987"
Test #24:
score: 0
Accepted
time: 0ms
memory: 5740kb
input:
1983
output:
571776252
result:
ok 1 number(s): "571776252"
Test #25:
score: 0
Accepted
time: 1ms
memory: 5716kb
input:
1992
output:
12983695
result:
ok 1 number(s): "12983695"
Subtask #6:
score: 15
Accepted
Test #26:
score: 15
Accepted
time: 1ms
memory: 5612kb
input:
3946
output:
977435333
result:
ok 1 number(s): "977435333"
Test #27:
score: 0
Accepted
time: 6ms
memory: 8336kb
input:
65944
output:
312666196
result:
ok 1 number(s): "312666196"
Test #28:
score: 0
Accepted
time: 12ms
memory: 10656kb
input:
163815
output:
163767254
result:
ok 1 number(s): "163767254"
Test #29:
score: 0
Accepted
time: 15ms
memory: 10272kb
input:
198732
output:
911833524
result:
ok 1 number(s): "911833524"
Test #30:
score: 0
Accepted
time: 19ms
memory: 7260kb
input:
199287
output:
910277128
result:
ok 1 number(s): "910277128"
Test #31:
score: 0
Accepted
time: 19ms
memory: 11128kb
input:
199819
output:
561747634
result:
ok 1 number(s): "561747634"
Subtask #7:
score: 30
Accepted
Test #32:
score: 30
Accepted
time: 30ms
memory: 10772kb
input:
315618
output:
602805814
result:
ok 1 number(s): "602805814"
Test #33:
score: 0
Accepted
time: 115ms
memory: 26640kb
input:
1130465
output:
898203793
result:
ok 1 number(s): "898203793"
Test #34:
score: 0
Accepted
time: 465ms
memory: 76804kb
input:
4399723
output:
101317224
result:
ok 1 number(s): "101317224"
Test #35:
score: 0
Accepted
time: 528ms
memory: 84132kb
input:
4804460
output:
114947085
result:
ok 1 number(s): "114947085"
Test #36:
score: 0
Accepted
time: 545ms
memory: 85876kb
input:
4995726
output:
460040939
result:
ok 1 number(s): "460040939"
Test #37:
score: 0
Accepted
time: 518ms
memory: 84936kb
input:
4999919
output:
780785591
result:
ok 1 number(s): "780785591"
Test #38:
score: 0
Accepted
time: 524ms
memory: 85020kb
input:
4999999
output:
742624725
result:
ok 1 number(s): "742624725"