Time limit: 3.000 seconds
限时: 3.000秒
Background
背景
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
问题
Given an integer n ≥ 1 and an integer p ≥ 1 you are to write a program that determines , the positive nth root of p. In this problem, given such integers n and p, p will always be of the form kn for an integer k (this integer is what your program must find).
The Input
输入
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 ≤ 10101and there exists an integer k, 1 ≤ k ≤ 109 such that kn = p.
The Output
输出
For each integer pair n and p the value should be printed, i.e., the number k such that kn = p.
Sample Input
2
16
3
27
7
4357186184021382204544
Sample Output
4
3
1234
Analysis
这道题刚一拿到手着实让我吓了一跳,难道是让我来实现大数的数值算法吗?我一开始想到了大整数运算,后来想到牛顿迭代法。最后发现给定的p值并没有超过double能表示的范围,汗……啥也不说了,看代码吧。
Solution
#include <iostream> #include <math.h> using namespace std; int main(void) { for (double dNum, dPow; cin >> dPow >> dNum; cout << (int)(pow(dNum, 1.0 / dPow) + 0.5) << endl); return 0; }
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作者:王雨濛;新浪微博:@吉祥村码农;来源:《程序控》博客 -- http://www.cnblogs.com/devymex/ 此文章版权归作者所有(有特别声明的除外),转载必须注明作者及来源。您不能用于商业目的也不能修改原文内容。 |