HDU2814 (Fibonacci sequence loop section + Euler function loop section)

It is known that F (n) is a Fibonacci sequence. Given a, B, n, c

 

Analysis: the original formula is equivalent to finding links.

#include <iostream>#include <string.h>#include <stdio.h>using namespace std;typedef unsigned long long LL;int c;LL a,b,n;LL f[5500];int search(int c){    int loop;    f[0]=0;f[1]=1;    for(int i=2;i<2005;i++)    {        f[i]=(f[i-1]%c+f[i-2]%c)%c;        if(f[i]==1&&f[i-1]==0)        {            loop=i;            break;        }    }    return loop-1;}int phi(int n){    int rea=n,i;    for(i=2;i*i<=n;i++)    {        if(n%i==0)        {            rea=rea-rea/i;            while(n%i==0) n/=i;        }    }    if(n>1)       rea=rea-rea/n;    return rea;}LL multi(LL a,LL b,LL m){    LL ans=0;    while(b)    {        if(b&1)        {            ans=(ans+a)%m;            b--;        }        b>>=1;        a=(a+a)%m;    }    return ans;}LL quick_mod(LL a,LL b,LL m){    LL ans=1;    a%=m;    while(b)    {        if(b&1)        {            ans=multi(ans,a,m);            b--;        }        b>>=1;        a=multi(a,a,m);    }    return ans;}int main(){    int t,tt=1;    LL tmp1,tmp2;    LL t1,t2;    scanf("%d",&t);    while(t--)    {        scanf("%I64u%I64u%I64u%d",&a,&b,&n,&c);        printf("Case %d: ",tt++);        if(c==1)        {            puts("0");            continue;        }        int p=phi(c);        int loop1=search(c);        t1=quick_mod(a,b,loop1);        tmp1=f[t1]%c;        int loop2=search(p);        t2=quick_mod(a,b,loop2);        tmp2=f[t2]%p;        tmp2=quick_mod(tmp2,n-1,p);        tmp2+=p;        tmp1=quick_mod(tmp1,tmp2,c);        printf("%I64u\n",tmp1);    }    return 0;}