POJ 1286 Necklaces of Beads (Burnside theorem, restricted type), pojburnside

POJ 1286 Necklaces of Beads (Burnside theorem, restricted type), pojburnside

Question link: http://vjudge.net/problem/viewProblem.action? Id = 11117

Is to calculate the number of combinations after the replacement section using each equivalent case.

#include <stdio.h>#include <cstring>#include <cstdlib>#include <algorithm>#include <cmath>           using namespace std;#define lson o<<1#define rson o<<1|1#define max(a,b) (a)>(b)?(a):(b)#define min(a,b) (a)<(b)?(a):(b)#define INF 200000000           typedef long long ll;ll qpow(ll a,int k){   ll ans=1;   while(k>0){     if(k&1)ans*=a;     a*=a;     k>>=1;   }   return ans;}int gcd(int a,int b){   if(a==0)return b;   return gcd(b%a,a);}ll rotation(int n){   ll rot=3;   for(int i=2;i<=n;i++){      rot+=qpow(3LL,gcd(i,n));   }   return rot;}ll reflection(int n){   ll ref=0;   if(n&1){      int cir=n/2+1;      ref=qpow(3LL,cir)*n;   }else{      ref=(ll)(n/2)*qpow(3LL,n/2);      ref+=(ll)(n/2)*qpow(3LL,1+n/2);   }   return ref;}           int main(){   int n;   while(~scanf("%d",&n) && n+1){      ll ans;      if(!n)ans=0;      else ans=(rotation(n)+reflection(n))/(2*n);      printf("%I64d\n",ans);   }   return 0;}