和容斥有点相似,代码看懂了,原理还不是很理解。
ll mod_pow(ll x,ll n,ll mod) { ll res = 1; while(n > 0) { if(n & 1) res = (res * x)%moder; x = (x*x)%moder; n >>= 1; } return res; } map<int,int> moebius(int n) { map<int,int>res; vector<int>primes; for(int i=2;i*i < n;i++) { if(n%i == 0) { primes.push_back(i); while(n%i ==0) n = n/i; } } if(n != 1)primes.push_back(n); int m = primes.size(); for(int i=0;i < (1 << m);i++) { int mu=1,d=1; for(int j=0;j < m;j++) { if(i << j & 1) { mu *= -1; d *= primes[j]; } } res[d] = mu; } return res; } int n; void solve() { int res = 0; map<int,int> mu = moebius(n); for(map<int,int>::iterator it = mu.begin();it != mu.end();++it) { res += it->second * mod_pow(26,n/it->first,moder); res = (res%moder+moder)%moder; } printf("%d ",res); }
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