uva 113 Power of Cryptography（double活用）

Power of Cryptography

Background

Current work in cryptography involves (among other things) large prime numbers and computing powers of numbers modulo functions of 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 of only theoretical interest.

This problem involves the efficient computation of integer roots of numbers.

The Problem

Given an integer 

 and an integer 

 you
are to write a program that determines 

 , the positive 

 root
of p. In this problem, given such integers n and p, p will always be of the form 

 for an integer k (this
integer is what your program must find).

The 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 

 ,

 and
there exists an integer k, 

 such that 

 .

The Output

For each integer pair n and p the value 

 should be printed, i.e., the number k such that 

 .

Sample Input

2
16
3
27
7
4357186184021382204544

Sample Output

4
3
1234

题目大意：k ^ n = q. 求n.

解题思路：double的上限是1.7e+308，完全够。

#include<stdio.h>
#include<math.h>
int main(){
double n, m;
while (scanf("%lf%lf", &n, &m) != EOF){
printf("%.lf\n", pow(m, 1 / n));
}
return 0;}