Submission #1210922

#	Time	Username	Problem	Language	Result	Execution time	Memory
1210922		loom	Cryptography (NOI20_crypto)	C++20	100 / 100	434 ms	23992 KiB

Crypto

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define nl '\n'

using namespace __gnu_pbds;
template<class T> using indexed_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const int mod = 1e9+7, N = 3e5;
int p[N], fact[N];

inline void solve(){
   int n;
   cin>>n;
   for(int i=0; i<n; i++) cin>>p[i];

   fact[0] = 1;
   for(int i=1; i<n; i++) fact[i] = fact[i-1] * i % mod;

   indexed_set<int> st;
   for(int i=0; i<n; i++) st.insert(p[i]);

   int ans = 1;
   for(int i=0; i<n; i++){
      ans += st.order_of_key(p[i]) * fact[n-i-1];
      ans %= mod;
      st.erase(p[i]);
   }

   cout<<ans;
}

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

   int t = 1;
   //cin>>t;
   while(t--) solve();

   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