#include <iostream>
using namespace std;
int N;
int A[10005];
int DP[10005];
int Fact[10005], Inv[10005];
const int MOD = 1000007;
int Power[10005];
int C[1005][1005];
int power(int n, int p)
{
int sol = 1;
while(p)
{
if(p % 2 == 1)
{
sol = (1LL * sol * n) % MOD;
}
p /= 2;
n = (1LL * n * n) % MOD;
}
return sol;
}
void Read()
{
cin >> N;
for(int i = 1; i <= N; i++)
cin >> A[i];
}
void precalcFact()
{
Fact[0] = 1;
for(int i = 1; i <= N; i++)
Fact[i] = (1LL * Fact[i - 1] * i) % MOD;
Inv[N] = power(Fact[N], MOD - 2);
for(int i = N - 1; i >= 0; i--)
{
Inv[i] = (1LL * Inv[i + 1] * (i + 1)) % MOD;
}
}
int Comb(int n, int k)
{
return C[n][k];
}
inline void Add(int& x, int y)
{
x += y;
if(x >= MOD)
x -= MOD;
}
void precalcDP()
{
DP[0] = 1;
for(int i = 1; i <= N; i++)
{
for(int j = 0; j < i; j++)
{
Add(DP[i], (1LL * DP[i - 1 - j] * Comb(i - 1, j)) % MOD);
}
}
}
void precalcComb()
{
for(int i = 0; i <= N; i++)
C[i][0] = 1;
for(int i = 1; i <= N; i++)
for(int j = 1; j <= i; j++)
{
C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
if(C[i][j] >= MOD)
C[i][j] -= MOD;
}
}
void Solve()
{
int nb = 1, ans = 1;
Power[0] = 1;
for(int j = 1; j <= N; j++)
Power[j] = j;
for(int i = 2; i <= N; i++)
{
if(A[i] == 1)
continue;
int aux = 0;
for(int j = 0; j <= N - i; j++)
{
Add(aux, (1LL * Comb(N - i, j) * DP[j] * Power[N - i - j]) % MOD);
}
Add(ans, (1LL * aux * (A[i] - 1)) % MOD);
if(A[i] == nb + 1)
{
for(int j = 1; j <= N - i; j++)
{
Power[j] = (1LL * Power[j] * j) % MOD;
}
++nb;
}
}
cout << ans << "\n";
}
int main()
{
Read();
precalcFact();
precalcComb();
precalcDP();
Solve();
//cout << DP[N] << "\n";
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
2 ms |
376 KB |
Output is correct |
2 |
Correct |
2 ms |
376 KB |
Output is correct |
3 |
Correct |
2 ms |
416 KB |
Output is correct |
4 |
Correct |
2 ms |
492 KB |
Output is correct |
5 |
Correct |
13 ms |
492 KB |
Output is correct |
6 |
Correct |
2 ms |
544 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
2 ms |
544 KB |
Output is correct |
2 |
Incorrect |
2 ms |
544 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
544 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
952 KB |
Output isn't correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
952 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
4 ms |
2540 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
10 ms |
4576 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
12 ms |
8940 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
10 ms |
9024 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
13 ms |
9172 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
2 |
Halted |
0 ms |
0 KB |
- |