#include <bits/stdc++.h>
using namespace std;
#define all(x) begin(x), end(x)
#define sz(x) ((int)size(x))
#define trace(x) cout << #x << ": " << (x) << endl;
typedef long long ll;
const int mod = 1'000'007;
int add(int a, int b) {
return a + b < mod ? a + b : a + b - mod;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<int> a(n);
for (int i = 0; i < n; ++i) {
cin >> a[i];
}
vector<vector<int>> dp(n + 1, vector<int>(n + 1));
//cnt, len
for (int cnt = n; cnt > -1; --cnt) {
dp[cnt][0] = 1;
for (int len = 1; len <= n; ++len) {
dp[cnt][len] = (dp[cnt][len - 1] * cnt + (cnt < n ? dp[cnt + 1][len - 1] : 0)) % mod;
}
}
int ans = 0;
int cnt = 0;
for (int i = 0; i < n; ++i) {
ans = (ans + dp[cnt][n - i - 1] * (a[i] - 1)) % mod;
cnt = max(cnt, a[i]);
}
cout << (ans + 1) % mod;
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
212 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
4 |
Correct |
1 ms |
212 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
320 KB |
Output is correct |
2 |
Correct |
0 ms |
316 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
340 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
340 KB |
Output is correct |
2 |
Correct |
1 ms |
340 KB |
Output is correct |
3 |
Correct |
1 ms |
316 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
3 ms |
1236 KB |
Output is correct |
2 |
Correct |
3 ms |
1236 KB |
Output is correct |
3 |
Correct |
3 ms |
1236 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
11 ms |
4200 KB |
Output is correct |
2 |
Correct |
10 ms |
4288 KB |
Output is correct |
3 |
Correct |
10 ms |
4284 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
32 ms |
65536 KB |
Execution killed with signal 9 |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
32 ms |
65536 KB |
Execution killed with signal 9 |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
32 ms |
65536 KB |
Execution killed with signal 9 |
2 |
Halted |
0 ms |
0 KB |
- |