扩展BSGS

https://codeforces.com/gym/101853/problem/G

当板子记住把

#include<bits/stdc++.h>
using namespace std;
const int MAX=5e5+10;
typedef long long ll;
ll BSGS(ll a,ll b,ll m)
{
    a%=m;
    b%=m;
    if(b==1)return 0;
    unordered_map<ll,ll>ma;
    ll n=sqrt(2*m)+1;
    ll e=1;
    for(int i=0;i<n;i++)
    {
        if(ma.count(b*e%m)==0)ma[b*e%m]=i;//很奇怪去掉ma.count(b*e%m)==0就会WA
        e=e*a%m;
    }
    ll t=1;
    for(int i=1;i<=n+1;i++)
    {
        t=t*e%m;
        if(ma.count(t))return i*n-ma[t];
    }
    return -1;
}
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        ll a,b,m;
        scanf("%lld%lld%lld",&a,&b,&m);
        printf("%lld\n",BSGS(a,b,m));
    }
    return 0;
}