• C. Primes and Multiplication(数学)(防止爆精度)


    C. Primes and Multiplication
    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Let's introduce some definitions that will be needed later.

    Let prime(x)prime(x) be the set of prime divisors of xx. For example, prime(140)={2,5,7}prime(140)={2,5,7}, prime(169)={13}prime(169)={13}.

    Let g(x,p)g(x,p) be the maximum possible integer pkpk where kk is an integer such that xx is divisible by pkpk. For example:

    • g(45,3)=9g(45,3)=9 (4545 is divisible by 32=932=9 but not divisible by 33=2733=27),
    • g(63,7)=7g(63,7)=7 (6363 is divisible by 71=771=7 but not divisible by 72=4972=49).

    Let f(x,y)f(x,y) be the product of g(y,p)g(y,p) for all pp in prime(x)prime(x). For example:

    • f(30,70)=g(70,2)g(70,3)g(70,5)=213051=10f(30,70)=g(70,2)⋅g(70,3)⋅g(70,5)=21⋅30⋅51=10,
    • f(525,63)=g(63,3)g(63,5)g(63,7)=325071=63f(525,63)=g(63,3)⋅g(63,5)⋅g(63,7)=32⋅50⋅71=63.

    You have integers xx and nn. Calculate f(x,1)f(x,2)f(x,n)mod(109+7)f(x,1)⋅f(x,2)⋅…⋅f(x,n)mod(109+7).

    Input

    The only line contains integers xx and nn (2x1092≤x≤109, 1n10181≤n≤1018) — the numbers used in formula.

    Output

    Print the answer.

    Examples
    input
    Copy
    10 2
    
    output
    Copy
    2
    
    input
    Copy
    20190929 1605
    
    output
    Copy
    363165664
    
    input
    Copy
    947 987654321987654321
    
    output
    Copy
    593574252
    
    Note

    In the first example, f(10,1)=g(1,2)g(1,5)=1f(10,1)=g(1,2)⋅g(1,5)=1, f(10,2)=g(2,2)g(2,5)=2f(10,2)=g(2,2)⋅g(2,5)=2.

    In the second example, actual value of formula is approximately 1.597101711.597⋅10171. Make sure you print the answer modulo (109+7)(109+7).

    In the third example, be careful about overflow issue.

    #include<iostream>
    #include<stdio.h>
    #include<algorithm>
    #include<math.h>
    using namespace std;
    typedef unsigned long long ll;
    ll fac[10050], num;//素因数,素因数的个数
    const ll mod=1e9+7;
     
    ll pow_mod(ll a, ll n, ll m)
    {
        if(n == 0) return 1;
        ll x = pow_mod(a, n/2, m);
        ll ans = (ll)x * x % m;
        if(n % 2 == 1) ans = ans *a % m;
        return (ll)ans;
    }
     
     
     
    void init(ll n) {//唯一分解定理
        num = 0;
        ll cpy = n;
        ll m = (int)sqrt(n + 0.5);
        for (int i = 2; i <= m; ++i) {
            if (cpy % i == 0) {
                fac[num++] = i;
                while (cpy % i == 0) cpy /= i;
            }
        }
        if (cpy > 1) fac[num++] = cpy;
    }
     
     
     
    int main(){
        ll x,n;
        cin>>x>>n;
        init(x);
        ll ans=1;
        for(ll i=0;i<num;i++){
            for(ll cur=fac[i];;cur*=fac[i]){
                ans=ans*pow_mod(fac[i],n/cur,mod)%mod;
                if(cur>n/fac[i]) break;
            }
        }
        cout<<ans%mod<<endl;
    } 
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  • 原文地址:https://www.cnblogs.com/ellery/p/11628053.html
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