Submission #329823

#	Time	Username	Problem	Language	Result	Execution time	Memory
329823		JiratQ	Cryptography (NOI20_crypto)	C++14	100 / 100	262 ms	35668 KiB

Crypto

#include<bits/stdc++.h>
#define int long long
using namespace std;
int dp[300010];
int fw[300010];

int fac(int n){
    if(dp[n]!=0) return dp[n];
    if(n==0) return 1;
    return dp[n]=(fac(n-1)%1000000007*n)%1000000007;
}

void update(int node,int val){
    while(node<300010){
        fw[node] += val;
        node += (node&-node);
    }
}

int qs(int node){
    int sum=0;
    while(node>0){
        sum += fw[node];
        node -= (node&-node);
    }
    return sum;
}

main(){
    int n;
    cin >> n;
    vector<int> vec;
    for(int i=0;i<n;i++){
        int k;
        scanf("%lld",&k);
        vec.emplace_back(k);
    }
    vector<int> v=vec;
    sort(v.begin(),v.end());
    unordered_map<int,int> mapp;
    int cnt=1;
    for(int i=0;i<n;i++){
        mapp[v[i]]=cnt;
        cnt++;
    }
    for(int i=0;i<n;i++){
        vec[i]=mapp[vec[i]];
    }
    int ans=1;
    for(int i=0;i<n;i++){
        int c=qs(vec[i]);
        update(vec[i],1);
        ans += ((vec[i]-1-c) * fac(n-1-i));
        ans %= 1000000007;
    }
    cout << ans;
}

Compilation message (stderr)

Crypto.cpp:29:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   29 | main(){
      |      ^
Crypto.cpp: In function 'int main()':
Crypto.cpp:35:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   35 |         scanf("%lld",&k);
      |         ~~~~~^~~~~~~~~~~

• 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