poj 2109 Power of Cryptography

Description

Current work in cryptography involves (among other things) large prime numbers and computing powers of numbers among these primes. Work in this area has resulted in the practical use of results from number theory and other branches of mathematics once considered to be only of theoretical interest.
This problem involves the efficient computation of integer roots of numbers.
Given an integer n>=1 and an integer p>= 1 you have to write a program that determines the n th positive root of p. In this problem, given such integers n and p, p will always be of the form k to the n^th. power, for an integer k (this integer is what your program must find).

Input

The input consists of a sequence of integer pairs n and p with each integer on a line by itself. For all such pairs 1<=n<= 200, 1<=p<10¹⁰¹ and there exists an integer k, 1<=k<=10⁹ such that kⁿ = p.

Output

For each integer pair n and p the value k should be printed, i.e., the number k such that k n =p.

Sample Input

2 16
3 27
7 4357186184021382204544

Sample Output

4
3
1234

类型	长度	有效数字	绝对值范围
float	32	6~7	10^(-37) ~ 10^38
double	64	15~16	10^(-307) ~ 10^308
long double	128	18~19	10^(-4931) ~ 10 ^ 4932

贪心？数据在double之内

double有效数字为15~16,为了避免double对输入的数在运算过程中进行精确，那么我们必须让double的运算第一步就得到一个int

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    double n,p;
    while(cin>>n>>p)
    {
        double k;
        k=pow(p,1/n);
        cout<<k<<endl;
    }
}