zoukankan      html  css  js  c++  java
  • Power of Cryptography

     
    Time Limit: 1000MS   Memory Limit: 30000K
    Total Submissions: 20351   Accepted: 10284

    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 nth. 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
    注:这题分类是贪心算法,但是看了discuss之后竟然发现用double一句可以AC,也是醉了
    k^n=p
    n=log(p)/log(k)
    log(k)=log(p)/n
    2^log(k)=2^(log(p)/n)
    k=p^(1/n)
    附:float,double,long double的范围
    类型          长度 (bit)           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
     1 #include<iostream>
     2 #include<math.h>
     3 using namespace std;
     4 
     5 
     6 int main()
     7 {
     8     double n,p;
     9     while(cin>>n>>p)
    10         cout<<pow(p,1.0/n)<<endl;  
    11     return 0;
    12 }
  • 相关阅读:
    IIS相关知识
    C#小知识
    DOS与批处理
    Visual Studio与Chrome调试工具使用技巧
    CLR via C# 随记
    jQuery Plugin Docs
    FlexPaper使用小结
    软件测试分为几个阶段 各阶段的测试策略和要求是什么?
    软件产品质量特性是什么?
    简述什么是静态测试、动态测试、黑盒测试、白盒测试、α测试 β测试
  • 原文地址:https://www.cnblogs.com/sdxk/p/4598506.html
Copyright © 2011-2022 走看看