Wannafly Winter Camp 2020 Day 5G Cryptographically Secure Pseudorandom Number Generator - 分块

A plurality of sets of data, given a prime \ (P \) , require that all \ (X \) such that \ (f (x) = \ min_ {K = 2} ^ XF (K) \) , where \ (f (x) = x ^ {- 1} \ )

All \ (P \) in ([1, 10 ^ 9] \) \ uniformly in the selected

Solution

Obviously inverse sequence symmetrical relationship

Thus the root of the enumeration, the back half of the symmetrical output to

Why is this my problem card for an hour :(

Beginning enumeration border written \ (\ sqrt p \) how would go through

I later found could be a brisk

#include <bits/stdc++.h>
using namespace std;

#define int long long

int a[1000005],p,t;

signed main() {
    ios::sync_with_stdio(false);
    cin>>t;
    while(t--) {
        cin>>p;
        vector <pair<int,int> > v;
        int lim=sqrt(p);
        a[1]=1;
        int mx=1e9,pos=1;
        for(int i=2;i<=p;i++) {
            a[i]=-(p/i)*a[p%i],
            a[i]=(a[i]%p+p)%p;
            if(i>=a[i]) break;
            mx=min(mx,a[i]);
            if(mx==a[i]) {
                if(i<a[i])
                    v.push_back(make_pair(i,a[i]));
            }
        }
        int flag=0;
        if(sqrt(p+1) == (int)sqrt(p+1)) flag=1;
        cout<<2*v.size()+flag<<endl;
        for(int i=0;i<v.size();i++) cout<<v[i].first<<" "<<v[i].second<<endl;
        if(flag) cout<<(int)sqrt(p+1)<<" "<<(int)sqrt(p+1)<<endl;
        for(int i=v.size()-1;i>=0;--i) cout<<v[i].second<<" "<<v[i].first<<endl;
    }
}