Submission #733816

#	Time	Username	Problem	Language	Result	Execution time	Memory
733816		vjudge1	Cryptography (NOI20_crypto)	C++17	100 / 100	130 ms	8004 KiB

Crypto

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr int mod = 1e9 + 7;
template <typename T>
struct fenwick_tree {
    int n;
    vector<T> bit;
    fenwick_tree(int _n) : n(_n), bit(n + 1) {
    }
    void apply(int p, T v) {
        for (int i = p + 1; i <= n; i += i & -i) {
            bit[i] += v;
        }
    }
    T query(int p) {
        T ans{};
        for (int i = p; i > 0; i -= i & -i) {
            ans += bit[i];
        }
        return ans;
    }
    T range_query(int l, int r) {
        return query(r) - query(l);
    }
};
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];
    }
    auto b = a;
    sort(b.begin(), b.end());
    for (int i = 0; i < n; i++) {
        a[i] = lower_bound(b.begin(), b.end(), a[i]) - b.begin();
    }
    vector<int> fac(n + 1);
    fac[0] = 1;
    for (int i = 1; i <= n; i++) {
        fac[i] = 1LL * fac[i - 1] * i % mod;
    }
    int ans = 1;
    fenwick_tree<int> fw(n);
    for (int i = 0; i < n; i++) {
        ans = (ans + 1LL * (a[i] + fw.range_query(a[i] + 1, n) - i) * fac[n - i - 1] % mod) % mod;
        fw.apply(a[i], 1);
    }
    cout << ans << "\n";
    return 6/22;
}

• 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