#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double ld;
const int MOD = 1e9 + 7;
const int base = 37;
const int MAXN = (int)1e4 + 7;
const int infint = (int)1e9;
const ll inf = (ll)1e18;
ll n, a[MAXN], dp[MAXN], tmp[MAXN], mx[MAXN];
int main()
{
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 0; i < n; i++)
cin >> a[i];
mx[0] = a[0];
for (int i = 1; i < n; i++)
mx[i] = max(mx[i - 1], a[i]);
for (int i = 0; i <= n; i++)
dp[i] = 1;
ll ans = a[n - 1] - 1;
for (int i = n - 2; i >= 0; i--)
{
for (int j = 0; j <= n; j++)
tmp[j] = (j * dp[j] % MOD + dp[j + 1]) % MOD;
for (int j = 0; j <= n; j++)
dp[j] = tmp[j];
for (int k = 1; k < a[i]; k++)
{
ll t = k;
if(i)
t = max(t, mx[i - 1]);
ans += dp[t], ans %= MOD;
}
}
cout << (ans + 1) % MOD;
}
# |
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 |
456 KB |
Output is correct |
4 |
Correct |
2 ms |
604 KB |
Output is correct |
5 |
Correct |
2 ms |
604 KB |
Output is correct |
6 |
Correct |
2 ms |
604 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
2 ms |
604 KB |
Output is correct |
2 |
Correct |
2 ms |
628 KB |
Output is correct |
3 |
Correct |
2 ms |
648 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
652 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
2 ms |
656 KB |
Output isn't correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
3 ms |
660 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
3 ms |
664 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
7 ms |
668 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
717 ms |
1060 KB |
Output isn't correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
109 ms |
1060 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
437 ms |
1136 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |