Submission #261291

#	Time	Username	Problem	Language	Result	Execution time	Memory
261291		Haunted_Cpp	Cryptography (NOI20_crypto)	C++17	100 / 100	170 ms	8084 KiB

Crypto

/**
 *  author: Haunted_Cpp
**/
 
#include <bits/stdc++.h>
using namespace std;
 
#pragma GCC optimize("Ofast")
#pragma GCC target("fma,sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#pragma GCC optimize("unroll-loops")
 
template<typename T> ostream &operator << (ostream &os, const vector<T> &v) { os << '{'; string sep; for (const auto &x : v) os << sep << x, sep = ", "; return os << '}'; }
template<typename T, size_t size> ostream &operator << (ostream &os, const array<T, size> &arr) { os << '{'; string sep; for (const auto &x : arr) os << sep << x, sep = ", "; return os << '}'; }
template<typename A, typename B> ostream &operator << (ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
 
void debug_out() { cerr << endl; }
template<typename Head, typename... Tail> void debug_out(Head H, Tail... T) { cerr << ' ' << H; debug_out(T...); }
 
#ifdef LOCAL
#define debug(...) cerr << "(" << #__VA_ARGS__ << "):", debug_out(__VA_ARGS__)
#else
#define debug(...) 47
#endif

const int MAX_N = 3e5 + 5;
const int MOD = 1e9 + 7;

int f[MAX_N], bit[MAX_N];

void update(int idx, int delta) {
  for (; idx < MAX_N; idx += idx & (- idx)) {
    bit[idx] += delta;
  }
}

int query(int idx) {
  int res = 0;
  for (; idx > 0; idx -= idx & (- idx)) {
    res += bit[idx];
  }
  return res;
}

int add(int a, int b) {
  int res = a + b;
  if (res >= MOD) res -= MOD;
  if (res < 0) res += MOD;
  return res;
}

int mult(int a, int b) {
  long long res = 1LL * a * b;
  if (res >= MOD) res %= MOD;
  return res;
}

int main () {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> arr(n);
  vector<int> c(n);
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    c[i] = arr[i];
  }
  sort(c.begin(), c.end());
  c.erase(unique(c.begin(), c.end()), c.end());
  for (auto &to : arr) {
    to = lower_bound(c.begin(), c.end(), to) - c.begin() + 1;
    update(to, +1);
  }
  f[0] = 1;
  for (int i = 1; i < MAX_N; i++) {
    f[i] = mult(f[i - 1], i);
  }
  int res = 0;
  int left = n - 1;
  for (int i = 0; i < n; left--, i++) {
    int l = query(arr[i] - 1);
    res = add(res, mult(l, f[left]));
    update(arr[i], -1);
  }
  cout << add(res, +1) << '\n';
  return 0;
}

• 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