Submission #539389

#	Time	Username	Problem	Language	Result	Execution time	Memory
539389		singlabharat	Cryptography (NOI20_crypto)	C++17	100 / 100	481 ms	29132 KiB

Crypto

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define int long long
using vi = vector<int>;
using vs = vector<string>;
using vb = vector<bool>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
using vpii = vector<pair<int, int>>;
using si = set<int>;
using mii = map<int, int>;
template<typename T> using pbds = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define sz(x) (int)size(x)
#define pb emplace_back
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define fr first
#define sc second
#define f(i, end) for (int i = 0; i < end; i++)
#define ff(i, start, end) for (int i = start; i < end; i++)
template<typename T, typename U> inline void domin(T &x, U y) {if (y < x) x = y;}
template<typename T, typename U> inline void domax(T &x, U y) {if (y > x) x = y;}
template<typename T, typename U> ostream& operator<<(ostream &os, const pair<T, U> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template < typename T_container, typename T = typename enable_if < !is_same<T_container, string>::value, typename T_container::value_type >::type > ostream & operator<<(ostream &os, const T_container &a) { os << '{'; string sep; for (const T &x : a) os << sep << x, sep = ", "; return os << '}';}
void debug() {cerr << endl;}
template <typename Head, typename... Tail> void debug(Head h, Tail... t) {cerr << h << ' '; debug(t...);}
#ifdef singlabharat
#define debug(...) cerr << "(" << #__VA_ARGS__ << ") : ", debug(__VA_ARGS__)
#else
#define debug(...)
#endif
#define endl '\n'
const int MX = 3e5 + 2, INF = 1e18, MOD = 1e9 + 7;

void solve() {

	vi fact(MX);
	fact[0] = 1;
	ff(i, 1, MX) fact[i] = (fact[i - 1] * i) % MOD;

	int n;
	cin >> n;
	vi a(n);
	f(i, n) cin >> a[i];

	pbds<int> os;
	vi dp(n + 1); //dp[i] -> #permutations of a[i..] <= a[i..]
	dp[n] = 1;
	for (int i = n - 1; i >= 0; i--) {
		dp[i] = os.order_of_key(a[i]) * fact[n - i - 1] + dp[i + 1];
		dp[i] %= MOD;
		os.insert(a[i]);
	}
	
	cout << dp[0];
}

int32_t main() {

#ifdef singlabharat
	freopen("error.txt", "w", stderr);
#endif

	cin.tie(0)->sync_with_stdio(0);

	int t = 1;
	// cin >> t;

	for (int tc = 0; tc < t; tc++) solve();
}

• Subtask 1: 5 / 5
• Subtask 2: 9 / 9
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 21 / 21
• Subtask 6: 13 / 13
• Subtask 7: 19 / 19
• Subtask 8: 12 / 12