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  • 【欧拉降幂】Super_log

    In Complexity theory, some functions are nearly O(1)O(1), but it is greater then O(1)O(1). For example, the complexity of a typical disjoint set is O(nα(n))O(nα(n)). Here α(n)α(n) is Inverse Ackermann Function, which growth speed is very slow. So in practical application, we often assume α(n) le 4α(n)4.

    However O(α(n))O(α(n)) is greater than O(1)O(1), that means if nn is large enough, α(n)α(n) can greater than any constant value.

    Now your task is let another slowly function log*log∗ xx reach a constant value bb. Here log*log∗ is iterated logarithm function, it means “the number of times the logarithm function iteratively applied on xx before the result is less than logarithm base aa”.

    Formally, consider a iterated logarithm function log_{a}^*loga

    Find the minimum positive integer argument xx, let log_{a}^* (x) ge bloga(x)b. The answer may be very large, so just print the result xx after mod mm.

    Input

    The first line of the input is a single integer T(Tle 300)T(T300) indicating the number of test cases.

    Each of the following lines contains 33 integers aa , bb and mm.

    1 le a le 10000001a1000000

    0 le b le 10000000b1000000

    1 le m le 10000001m1000000

    Note that if a==1, we consider the minimum number x is 1.

    Output

    For each test case, output xx mod mm in a single line.

    Hint

    In the 4-th4th query, a=3a=3 and b=2b=2. Then log_{3}^* (27) = 1+ log_{3}^* (3) = 2 + log_{3}^* (1)=3+(-1)=2 ge blog3(27)=1+log3(3)=2+log3(1)=3+(1)=2b, so the output is 2727 mod 16 = 1116=11.

    样例输入

    5
    2 0 3
    3 1 2
    3 1 100
    3 2 16
    5 3 233

    样例输出

    1
    1
    3
    11
    223

    题解:求a^a^...(b次)%n的结果。因为n与a不一定互质,所以要利用广义欧拉定理进行降幂。

    AC代码:

    #include<iostream>
    #include<algorithm>
    #include<cstdio>
    #include<cstring>
    #include<queue>
    #include<set>
    #include<cmath>
    #include<string>
    #include<map>
    #include<vector>
    #include<ctime>
    #include<stack>
    using namespace std;
    #define mm(a,b) memset(a,b,sizeof(a))
    typedef long long ll;
    typedef unsigned long long ull;
    const int maxn = 2e5 + 10;
    #define inf 0x3f3f3f3f
    const double PI = acos(-1.0);
    
    ll gcd(ll a,ll b){return b==0?a:gcd(b,a%b);}
    
    #define Mod(a,b) a<b?a:a%b+b  //根据欧拉定理重定义mod
    
    ll fpow(ll a,ll n,ll mod)
    {
        ll res=1;
        while(n)
        {
            if(n&1) res=Mod(res*a,mod);
            a=Mod(a*a,mod);
            n>>=1;
        }
        return res;
    }
    
    ll phi(ll x)  //求x的欧拉函数
    {
        ll ans=x,tp=sqrt(x);
        for(ll i=2;i<=tp;++i)
        {
            if(x%i==0)
            {
                ans=ans-ans/i;
                while(x%i==0) x/=i;
            }
        }
        if(x>1) ans=ans-ans/x;
        return ans;
    }
    
    ll solve(ll a,ll b,ll m)
    {
        if(m==1) return 0;
        if(b<=1) return fpow(a,b,m);
        ll p=phi(m);
        ll t=solve(a,b-1,p);  //递归求解
        ll g=gcd(a,m);
        if(g==1||b<p) return fpow(a,t,m);
        else return fpow(a,t+p,m);
    }
    
    int main()
    {
        int T;
        scanf("%d",&T);
        while(T--)
        {
            ll a,b,m;
            scanf("%lld %lld %lld",&a,&b,&m);
            ll ans=solve(a,b,m)%m;
            printf("%lld
    ",ans);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/Tangent-1231/p/11459934.html
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