Submission #951204

#	Time	Username	Problem	Language	Result	Execution time	Memory
951204		NourWael	Cryptography (NOI20_crypto)	C++17	100 / 100	422 ms	27032 KiB

Crypto

#include <bits/extc++.h>
#define int long long
using namespace std; 
using namespace __gnu_pbds; 
int const mxN = 3e5+5;
int const mod = 1e9+7;
int perm[mxN], a[mxN];

signed main() {
  
  ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);

  int n; cin>>n;
  perm[1] = 1;
  for(int i=2; i<=n; i++) perm[i] = (perm[i-1] * i) % mod;
  
  tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> st;
  for(int i=0; i<n; i++) { cin>>a[i]; st.insert(a[i]); }
  
  int ans = 0;
  for(int i=0; i<n; i++) {
     int t = st.order_of_key(a[i]);
     ans += (t*perm[n-i-1])%mod;
     ans%=mod;
     st.erase(a[i]);
  }

  cout<<(ans+1)%mod;
   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