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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#448958 | #8526. Polygon II | 2745518585 | WA | 0ms | 1664kb | C++20 | 1.9kb | 2024-06-20 14:37:52 | 2024-06-20 14:37:52 |
Judging History
answer
#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N=2001,M=51;
const ll P=1e9+7;
int n,a[N],b[N];
ll jc[N],ivjc[N],pw[N],ivpw[N],f[N],g[N];
void exgcd(ll a,ll b,ll &x,ll &y)
{
if(b==0) x=1,y=0;
else exgcd(b,a%b,y,x),y-=a/b*x;
}
ll inv(ll a)
{
ll x,y;
exgcd(a,P,x,y);
x=(x%P+P)%P;
return x;
}
ll A(ll a,ll b)
{
if(a<b) return 0;
return jc[a]*ivjc[a-b]%P;
}
ll C(ll a,ll b)
{
if(a<b) return 0;
return jc[a]*ivjc[a-b]%P*ivjc[b]%P;
}
ll qpow(ll a,ll b)
{
ll x=1,y=a;
while(b)
{
if(b&1) x=x*y%P;
y=y*y%P;
b>>=1;
}
return x;
}
int main()
{
int n;
scanf("%d",&n);
jc[0]=1;
for(int i=1;i<=n+1;++i) jc[i]=jc[i-1]*i%P;
ivjc[n+1]=inv(jc[n+1]);
for(int i=n+1;i>=1;--i) ivjc[i-1]=ivjc[i]*i%P;
pw[0]=1;
for(int i=1;i<=n+1;++i) pw[i]=pw[i-1]*2%P;
ivpw[n+1]=inv(pw[n+1]);
for(int i=n+1;i>=1;--i) ivpw[i-1]=ivpw[i]*2%P;
for(int i=1;i<=n;++i)
{
int x;
scanf("%d",&x);
++a[x];
}
for(int i=50;i>=0;--i)
{
a[i]+=a[i+1];
b[i]=b[i+1]+a[i];
}
ll s=0;
for(int i=0;i<=n;++i)
{
f[i]=1;
for(int j=0;j<=min(n,i);++j)
{
f[i]=(f[i]-(j&1?-1:1)*C(n,j)%P*qpow(i-j,n)%P*ivjc[n]%P)%P;
}
}
for(int i=0;i<=n;++i) f[i]=(f[i]-f[i+1])%P;
for(int i=0;i<=30;++i)
{
for(int j=0;j<=n+1;++j) g[j]=f[j],f[j]=0;
for(int j=0;j<=n+1;++j)
{
for(int k=0;k<=a[i];++k)
{
f[(j+k)/2]=(f[(j+k)/2]+g[j]*C(a[i],k)%P*ivpw[a[i]]%P)%P;
}
}
for(int j=0;j<=n+1;++j) f[j]=(f[j]%P+P)%P;
s=(s+f[0]*ivpw[b[i+1]]%P*(a[i]-a[i+1])%P)%P;
}
printf("%lld",((1-s)%P+P)%P);
return 0;
}
Details
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Test #1:
score: 100
Accepted
time: 0ms
memory: 1644kb
input:
3 0 2 0
output:
166666668
result:
ok 1 number(s): "166666668"
Test #2:
score: 0
Accepted
time: 0ms
memory: 1632kb
input:
3 0 0 0
output:
500000004
result:
ok 1 number(s): "500000004"
Test #3:
score: 0
Accepted
time: 0ms
memory: 1564kb
input:
3 5 6 7
output:
208333335
result:
ok 1 number(s): "208333335"
Test #4:
score: -100
Wrong Answer
time: 0ms
memory: 1664kb
input:
3 0 25 50
output:
1
result:
wrong answer 1st numbers differ - expected: '889268532', found: '1'