// Om Namah Shivaya
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a, b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a, b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
*/
const int MOD = 1000007;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
void solve(int test_case)
{
ll n; cin >> n;
vector<ll> a(n + 5);
rep1(i, n) cin >> a[i];
assert(a[1] == 1);
ll dp1[n + 5][2], dp2[n + 5][2];
memset(dp1, 0, sizeof dp1);
memset(dp2, 0, sizeof dp2);
dp1[1][1] = 1;
for (int i = 2; i <= n; ++i) {
ll d = a[i];
rep1(j, n + 1) {
rep(t, 2) {
// < d
{
ll cnt = min((ll) j, d - 1);
dp2[j][0] += dp1[j][t] * cnt;
if (j + 1 < d) {
dp2[j + 1][0] += dp1[j][t];
}
}
// = d
if (d <= j) {
dp2[j][t] += dp1[j][t];
}
else if (d == j + 1) {
dp2[j + 1][t] += dp1[j][t];
}
// > d
if (!t) {
ll cnt = j - min((ll) j, d);
dp2[j][0] += dp1[j][t] * cnt;
if (j + 1 > d) {
dp2[j + 1][0] += dp1[j][t];
}
}
}
}
rep1(j, n + 1) {
rep(t, 2) {
dp1[j][t] = dp2[j][t] % MOD;
dp2[j][t] = 0;
}
}
}
ll ans = 0;
rep1(j, n + 1) {
rep(t, 2) {
ans = (ans + dp1[j][t]) % MOD;
}
}
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
212 KB |
Output is correct |
2 |
Correct |
0 ms |
212 KB |
Output is correct |
3 |
Correct |
0 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
212 KB |
Output is correct |
5 |
Correct |
0 ms |
212 KB |
Output is correct |
6 |
Correct |
0 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 |
212 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
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 |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
1 ms |
212 KB |
Output is correct |
# |
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 |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
3 ms |
212 KB |
Output is correct |
2 |
Correct |
4 ms |
212 KB |
Output is correct |
3 |
Correct |
3 ms |
320 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
9 ms |
320 KB |
Output is correct |
2 |
Correct |
8 ms |
360 KB |
Output is correct |
3 |
Correct |
10 ms |
340 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
770 ms |
732 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
184 ms |
508 KB |
Output is correct |
2 |
Correct |
210 ms |
508 KB |
Output is correct |
3 |
Correct |
173 ms |
468 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
692 ms |
724 KB |
Output is correct |
2 |
Correct |
734 ms |
724 KB |
Output is correct |
3 |
Correct |
719 ms |
732 KB |
Output is correct |