#include<bits/stdc++.h>
using namespace std;
const int maxn=605,tmaxn=1205;
int mod=1e9+7;
long long mypow(long long m,long long y){
if(y==0){
return 1;
}
long long p=mypow(m,(y>>1));
p*=p;
p%=mod;
if(y&1){
p*=m;
p%=mod;
}
return p;
}
int fact[tmaxn],revfact[tmaxn],magemishe[tmaxn],res[tmaxn][tmaxn],dp[tmaxn],n;
int vas[tmaxn];
int ww(int a){
if(a>=mod){
a-=mod;
}
return a;
}
void aval(){
fact[0]=1;
for(int i=1;i<tmaxn;i++){
fact[i]=1ll*fact[i-1]*i%mod;
}
revfact[tmaxn-1]=mypow(fact[tmaxn-1],mod-2);
for(int i=tmaxn-2;i>=0;i--){
revfact[i]=1ll*revfact[i+1]*(i+1)%mod;
}
}
inline int c(int i,int j){
if(i<0||j<0||j>i){
return 0;
}
int ret=1ll*fact[i]*revfact[j]%mod*revfact[i-j]%mod;
return ret;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
aval();
cin>>n;
for(int i=0;i<n;i++){
int d;
cin>>d;
vas[d]=1;
}
dp[0]=1;
for(int i=1;i<=n;i++){
for(int j=1;j<=i;j++){
dp[i]+=1ll*c(i-1,j-1)*(i-j+2)%mod*dp[i-j]%mod*dp[j-1]%mod;
dp[i]=ww(dp[i]);
}
}
res[n*2+1][0]=1;
int oomade=0,naumade=0;
for(int i=n*2;i>=1;i--){
if(vas[i]){
for(int j=0;j<=oomade+1;j++){
res[i][j]=res[i+1][j];
for(int h=1;h<=j;h++){
res[i][j]+=1ll*res[i+1][h-1]*dp[j-h]%mod*c(oomade-h+1,j-h)%mod*(j-h+2)%mod;
res[i][j]=ww(res[i][j]);
}
}
oomade++;
}
else{
for(int j=0;j<=oomade;j++){
res[i][j]=1ll*res[i+1][j]*max(j-naumade,0)%mod;
}
naumade++;
}
}
int mainres=1ll*res[1][n]*mypow(mypow(2,n),mod-2)%mod;
cout<<mainres<<"\n";
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
340 KB |
Output is correct |
2 |
Correct |
1 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
340 KB |
Output is correct |
4 |
Correct |
1 ms |
340 KB |
Output is correct |
5 |
Correct |
0 ms |
340 KB |
Output is correct |
6 |
Correct |
1 ms |
340 KB |
Output is correct |
7 |
Correct |
1 ms |
340 KB |
Output is correct |
8 |
Correct |
0 ms |
340 KB |
Output is correct |
9 |
Correct |
1 ms |
340 KB |
Output is correct |
10 |
Correct |
1 ms |
340 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
340 KB |
Output is correct |
2 |
Correct |
1 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
340 KB |
Output is correct |
4 |
Correct |
1 ms |
340 KB |
Output is correct |
5 |
Correct |
0 ms |
340 KB |
Output is correct |
6 |
Correct |
1 ms |
340 KB |
Output is correct |
7 |
Correct |
1 ms |
340 KB |
Output is correct |
8 |
Correct |
0 ms |
340 KB |
Output is correct |
9 |
Correct |
1 ms |
340 KB |
Output is correct |
10 |
Correct |
1 ms |
340 KB |
Output is correct |
11 |
Correct |
2 ms |
724 KB |
Output is correct |
12 |
Correct |
2 ms |
724 KB |
Output is correct |
13 |
Correct |
2 ms |
724 KB |
Output is correct |
14 |
Correct |
2 ms |
724 KB |
Output is correct |
15 |
Correct |
2 ms |
724 KB |
Output is correct |
16 |
Correct |
2 ms |
724 KB |
Output is correct |
17 |
Correct |
2 ms |
724 KB |
Output is correct |
18 |
Correct |
2 ms |
852 KB |
Output is correct |
19 |
Correct |
2 ms |
852 KB |
Output is correct |
20 |
Correct |
2 ms |
852 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
340 KB |
Output is correct |
2 |
Correct |
1 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
340 KB |
Output is correct |
4 |
Correct |
1 ms |
340 KB |
Output is correct |
5 |
Correct |
0 ms |
340 KB |
Output is correct |
6 |
Correct |
1 ms |
340 KB |
Output is correct |
7 |
Correct |
1 ms |
340 KB |
Output is correct |
8 |
Correct |
0 ms |
340 KB |
Output is correct |
9 |
Correct |
1 ms |
340 KB |
Output is correct |
10 |
Correct |
1 ms |
340 KB |
Output is correct |
11 |
Correct |
2 ms |
724 KB |
Output is correct |
12 |
Correct |
2 ms |
724 KB |
Output is correct |
13 |
Correct |
2 ms |
724 KB |
Output is correct |
14 |
Correct |
2 ms |
724 KB |
Output is correct |
15 |
Correct |
2 ms |
724 KB |
Output is correct |
16 |
Correct |
2 ms |
724 KB |
Output is correct |
17 |
Correct |
2 ms |
724 KB |
Output is correct |
18 |
Correct |
2 ms |
852 KB |
Output is correct |
19 |
Correct |
2 ms |
852 KB |
Output is correct |
20 |
Correct |
2 ms |
852 KB |
Output is correct |
21 |
Correct |
1079 ms |
5772 KB |
Output is correct |
22 |
Correct |
1082 ms |
5832 KB |
Output is correct |
23 |
Correct |
1098 ms |
5908 KB |
Output is correct |
24 |
Correct |
1087 ms |
5968 KB |
Output is correct |
25 |
Correct |
1081 ms |
5856 KB |
Output is correct |
26 |
Correct |
1079 ms |
5852 KB |
Output is correct |
27 |
Correct |
1084 ms |
5796 KB |
Output is correct |
28 |
Correct |
1079 ms |
5992 KB |
Output is correct |
29 |
Correct |
1077 ms |
5508 KB |
Output is correct |
30 |
Correct |
1393 ms |
6004 KB |
Output is correct |
31 |
Correct |
1235 ms |
5920 KB |
Output is correct |
32 |
Correct |
1311 ms |
5892 KB |
Output is correct |
33 |
Correct |
1371 ms |
5952 KB |
Output is correct |
34 |
Correct |
1234 ms |
5828 KB |
Output is correct |
35 |
Correct |
1307 ms |
5888 KB |
Output is correct |
36 |
Correct |
1370 ms |
5824 KB |
Output is correct |