#include <bits/stdc++.h>
#define MOD 1000000007
using namespace std;
unordered_map<int,int>ma;
long long putere(long long a,long long b)
{
if(b==0)
return 1;
long long p=putere(a,b/2);
p*=p;
p%=MOD;
if(b%2)
{
p*=a;
p%=MOD;
}
return p;
}
int fact[610],comb[610][610];
void factorial()
{
fact[0]=1;
for(long long i=1;i<=600;++i)
fact[i]=fact[i-1]*i%MOD;
}
long long combinari(long long n,long long m)
{
long long ans=1;
ans=fact[n];
ans*=putere(fact[m],MOD-2);
ans%=MOD;
ans*=putere(fact[n-m],MOD-2);
ans%=MOD;
return ans;
}
int n,v[610];
int cod(int step,int nrstack,int ppoz,bool exista)
{
return ((step*601+nrstack)*600+ppoz-1)*2+exista-1;
}
long long raspunde(int step,int nrstack,int ppoz,bool exista)
{
if(ma.find(cod(step,nrstack,ppoz,exista))!=ma.end())
return ma[cod(step,nrstack,ppoz,exista)];
if(step==n)
{
ma[cod(step,nrstack,ppoz,exista)]=1;
return 1;
}
int ans=0;
int ramas=n-step-nrstack;
int posibileInceput=v[ppoz]-1-(2*step-step+ppoz-1-nrstack);
if(exista==false)
{
if(ramas>=3)
ans=(1LL*ans+1LL*comb[ramas-1][2]*raspunde(step+1,nrstack+1,ppoz,false))%MOD;
if(ramas>=2)
ans=(1LL*ans+1LL*(ramas-1)*raspunde(step+1,nrstack+1,ppoz,true))%MOD;
if(posibileInceput>=2&&nrstack>=1)
ans=(1LL*ans+1LL*comb[posibileInceput][2]*raspunde(step+1,nrstack-1,ppoz,false))%MOD;
if(posibileInceput&&nrstack>=1&&ramas>=1)
{
if(ramas-1)
ans=(1LL*ans+1LL*posibileInceput*(ramas-1)%MOD*raspunde(step+1,nrstack,ppoz,false))%MOD;
ans=(1LL*ans+1LL*posibileInceput*raspunde(step+1,nrstack,ppoz,true))%MOD;
}
else if(posibileInceput&&ramas>=1)
{
if(step==n-1)
{
ma[cod(step,nrstack,ppoz,exista)]=1;
return 1;
}
if(ramas-1)
ans=(1LL*ans+1LL*posibileInceput*(ramas-1)%MOD*raspunde(step+1,nrstack,ppoz,false))%MOD;
int q=putere(comb[n-ppoz][step+1-ppoz],MOD-2);
for(int newppoz=ppoz+1;newppoz<=step+2;++newppoz)
ans=(1LL*ans+1LL*comb[n-newppoz][step+2-newppoz]*q%MOD*posibileInceput%MOD*raspunde(step+1,nrstack,newppoz,false))%MOD;
}
}
else
{
if(ramas>=2)
ans=(1LL*ans+1LL*comb[ramas][2]*raspunde(step+1,nrstack+1,ppoz,true))%MOD;
if(posibileInceput>=2)
{
if(nrstack>=2)
ans=(1LL*ans+1LL*comb[posibileInceput][2]*raspunde(step+1,nrstack-1,ppoz,true))%MOD;
else
{
if(step==n-1)
{
ma[cod(step,nrstack,ppoz,exista)]=1;
return 1;
}
int q=putere(comb[n-ppoz][step+1-ppoz],MOD-2);
for(int newppoz=ppoz+1;newppoz<=step+2;++newppoz)
ans=(1LL*ans+1LL*comb[n-newppoz][step+2-newppoz]*q%MOD*comb[posibileInceput][2]%MOD*raspunde(step+1,nrstack-1,newppoz,false))%MOD;
}
}
if(posibileInceput&&ramas>=1)
ans=(1LL*ans+1LL*posibileInceput*ramas%MOD*raspunde(step+1,nrstack,ppoz,true))%MOD;
}
ma[cod(step,nrstack,ppoz,exista)]=ans;
return ans;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
factorial();
cin>>n;
for(int i=1;i<=n;++i)
cin>>v[i];
for(int i=0;i<=n;++i)
for(int j=0;j<=i;++j)
comb[i][j]=combinari(i,j);
cout<<raspunde(0,0,1,false);
return 0;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
224 KB |
Output is correct |
2 |
Correct |
0 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
340 KB |
Output is correct |
4 |
Correct |
0 ms |
340 KB |
Output is correct |
5 |
Correct |
1 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 |
1 ms |
340 KB |
Output is correct |
9 |
Correct |
0 ms |
340 KB |
Output is correct |
10 |
Correct |
1 ms |
340 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
224 KB |
Output is correct |
2 |
Correct |
0 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
340 KB |
Output is correct |
4 |
Correct |
0 ms |
340 KB |
Output is correct |
5 |
Correct |
1 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 |
1 ms |
340 KB |
Output is correct |
9 |
Correct |
0 ms |
340 KB |
Output is correct |
10 |
Correct |
1 ms |
340 KB |
Output is correct |
11 |
Correct |
4 ms |
1108 KB |
Output is correct |
12 |
Correct |
3 ms |
980 KB |
Output is correct |
13 |
Correct |
6 ms |
1108 KB |
Output is correct |
14 |
Correct |
3 ms |
1040 KB |
Output is correct |
15 |
Correct |
1 ms |
468 KB |
Output is correct |
16 |
Correct |
2 ms |
596 KB |
Output is correct |
17 |
Correct |
1 ms |
468 KB |
Output is correct |
18 |
Correct |
10 ms |
1968 KB |
Output is correct |
19 |
Correct |
8 ms |
1968 KB |
Output is correct |
20 |
Correct |
8 ms |
1840 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
224 KB |
Output is correct |
2 |
Correct |
0 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
340 KB |
Output is correct |
4 |
Correct |
0 ms |
340 KB |
Output is correct |
5 |
Correct |
1 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 |
1 ms |
340 KB |
Output is correct |
9 |
Correct |
0 ms |
340 KB |
Output is correct |
10 |
Correct |
1 ms |
340 KB |
Output is correct |
11 |
Correct |
4 ms |
1108 KB |
Output is correct |
12 |
Correct |
3 ms |
980 KB |
Output is correct |
13 |
Correct |
6 ms |
1108 KB |
Output is correct |
14 |
Correct |
3 ms |
1040 KB |
Output is correct |
15 |
Correct |
1 ms |
468 KB |
Output is correct |
16 |
Correct |
2 ms |
596 KB |
Output is correct |
17 |
Correct |
1 ms |
468 KB |
Output is correct |
18 |
Correct |
10 ms |
1968 KB |
Output is correct |
19 |
Correct |
8 ms |
1968 KB |
Output is correct |
20 |
Correct |
8 ms |
1840 KB |
Output is correct |
21 |
Correct |
696 ms |
163568 KB |
Output is correct |
22 |
Correct |
520 ms |
113024 KB |
Output is correct |
23 |
Correct |
560 ms |
112916 KB |
Output is correct |
24 |
Correct |
1002 ms |
226780 KB |
Output is correct |
25 |
Correct |
78 ms |
1720 KB |
Output is correct |
26 |
Correct |
76 ms |
1792 KB |
Output is correct |
27 |
Correct |
76 ms |
1704 KB |
Output is correct |
28 |
Correct |
125 ms |
21116 KB |
Output is correct |
29 |
Correct |
75 ms |
1720 KB |
Output is correct |
30 |
Runtime error |
3218 ms |
524288 KB |
Execution killed with signal 9 |
31 |
Halted |
0 ms |
0 KB |
- |