题目不难 有个好的细节想着分享一下

一开始写的有点问题～需要特判掉一个...

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e5+10;const ll mod  = 998244353;ll qmi(ll a,ll b){ll ans = 1;while(b){if(b&1)ans = ans*a%mod;a = a*a%mod;b>>=1;}return (ans%mod+mod)%mod;
}ll inv(ll t){//if(t==998244353)return 1;return qmi(t,mod-2);
}void solve()
{ll a,b;cin>>a>>b;if(a==1&&b==1){cout<<0;return;}if(a==998244353&&b==1){cout<<998244352<<"\n";return;}ll tema = a;ll reu = 1;ll reu2 = 1;for(int i=2;i<=a/i;++i){if(a%i==0){reu  = (reu*(i-1)%mod+mod)%mod;while(a%i==0)a/=i;reu2 = reu2*i;}}if(a>1)reu = (reu*(a-1)%mod+mod)%mod,reu2 = reu2*a;//cout<<reu<<" "<<reu2<<"\n";reu2 = inv(reu2);
//	cout<<reu2<<"\n";reu = reu*reu2%mod;cout<<(qmi(tema,b)*reu%mod+mod)%mod;}int main()
{ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);int _;_ = 1;while(_--)solve();
}

题目很好写，但是这个算的思路需要借鉴一下

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e5+10;const ll mod  = 998244353;ll qmi(ll a,ll b){Sll ans = 1;while(b){if(b&1)ans = ans*a%mod;a = a*a%mod;b>>=1;}return (ans%mod+mod)%mod;
}void solve()
{ll a,b;cin>>a>>b;if(a==1){cout<<0;return;}ll tema = a;ll reu = a;for(int i=2;i<=a/i;++i){if(a%i==0){reu = reu*(i-1)/i;while(a%i==0)a/=i;}}if(a>1)reu = reu*(a-1)/a;cout<<qmi(tema,b-1)*reu%mod;}int main()
{ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);int _;_ = 1;while(_--)solve();
}