#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 Nb[10005];
int C[2][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;
Nb[1] = 1;
for(int i = 2; i <= N; i++)
{
if(A[i] == Nb[i - 1] + 1)
Nb[i] = Nb[i - 1] + 1;
else
Nb[i] = Nb[i - 1];
}
int ind = 0;
C[0][0] = 1;
for(int i = N; i >= 2; i--, ind = 1 - ind)
{
if(A[i] == 1)
continue;
int aux = 0;
int pw = 1;
if(i < N)
{
for(int j = N - i; j >= 1; j--)
{
C[ind][j] = C[1 - ind][j - 1];
Add(C[ind][j], C[1 - ind][j]);
}
C[ind][0] = 1;
int x = N - i;
for(int j = 0; j < x; j++)
{
Add(DP[x], (1LL * DP[x - 1 - j] * C[1 - ind][j]) % MOD);
}
}
for(int j = N - i; j >= 0; j--)
{
Add(aux, (1LL * C[ind][j] * DP[j] * pw) % MOD);
pw = (1LL * pw * Nb[i - 1]) % MOD;
}
Add(ans, (1LL * aux * (A[i] - 1)) % MOD);
}
cout << ans << "\n";
}
int main()
{
Read();
precalcFact();
// precalcComb();
precalcDP();
Solve();
//cout << DP[N] << "\n";
return 0;
}
Compilation message
teams.cpp: In function 'void Solve()':
teams.cpp:78:9: warning: unused variable 'nb' [-Wunused-variable]
int nb = 1, ans = 1;
^~
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
2 ms |
248 KB |
Output is correct |
2 |
Correct |
1 ms |
484 KB |
Output is correct |
3 |
Correct |
2 ms |
484 KB |
Output is correct |
4 |
Correct |
2 ms |
484 KB |
Output is correct |
5 |
Correct |
2 ms |
512 KB |
Output is correct |
6 |
Correct |
2 ms |
512 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
2 ms |
512 KB |
Output is correct |
2 |
Incorrect |
2 ms |
648 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
648 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
2 ms |
700 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
2 ms |
764 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 |
2 ms |
872 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 |
3 ms |
876 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 |
6 ms |
1048 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
4 ms |
1048 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 |
4 ms |
1064 KB |
Execution killed with signal 11 (could be triggered by violating memory limits) |
2 |
Halted |
0 ms |
0 KB |
- |