Template-prefix least common multiple of special sequence

形如: {   f ( 0 ) = 0   f ( 1 ) = 1   f ( n ) = a f ( n − 2 ) + b f ( n − 1 )              ( a , b ) = 1 \small \begin{cases} \ f(0)=0\\ \ f(1)=1\\ \ f(n)=af(n-2)+bf(n-1)~~~~~~~~~~~~(a,b)=1\\ \end{cases}  f(0)=0 f(1)=1 f(n)=a f ( n2)+bf(n1)            (a,b)=1
The least common multiple of the prefix of such a sequence can be in O (nlogn) \small O(nlogn)Obtain the complexity of O ( n l o g n ) .

#include<iostream>
using namespace std;

typedef long long ll;
const ll mod = 1e9 + 7;
const int maxn = 1e6 + 10;

//初始化数组
ll f[maxn] = {
    
     0,1 };

//求逆元
ll quick_pow(ll a, ll b) {
    
    
	ll res = 1;
	while (b) {
    
    
		if (b & 1) {
    
    
			res = (res * a) % mod;
		}
		a = (a * a) % mod;
		b >>= 1;
	}
	return res;
}

int main() {
    
    

	ll a, b, n;
	cin >> a >> b >> n;

	for (ll i = 2; i <= n; i++) {
    
    
		f[i] = (a * f[i - 2] + b * f[i - 1]) % mod;
	}

	for (ll i = 2; i <= n; i++) {
    
    
		ll inv = quick_pow(f[i], mod - 2);
		for (ll j = 2 * i; j <= n; j += i) {
    
    
			f[j] = (f[j] * inv) % mod;
		}
	}

	for (ll i = 2; i <= n; i++) {
    
    
		f[i] = (f[i - 1] * f[i]) % mod;
	}

	for (ll i = 1; i <= n; i++) {
    
    
		cout << f[i] << " ";
	}
	cout << endl;
	return 0;
}

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Origin blog.csdn.net/qq_45739057/article/details/106346353