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  • 1015 Reversible Primes (20 分)(素数)

    A reversible prime in any number system is a prime whose "reverse" in that number system is also a prime. For example in the decimal system 73 is a reversible prime because its reverse 37 is also a prime.

    Now given any two positive integers N (< 105) and D (1 < D <= 10), you are supposed to tell if N is a reversible prime with radix D.

    Input Specification:

    The input file consists of several test cases. Each case occupies a line which contains two integers N and D. The input is finished by a negative N.

    Output Specification:

    For each test case, print in one line "Yes" if N is a reversible prime with radix D, or "No" if not.

    Sample Input:

    73 10
    23 2
    23 10
    -2

    Sample Output:

    Yes
    Yes
    No

    生词

    英文 解释
    reversible 可逆的
    radix 进制

    题目大意:

    如果一个数本身是素数,而且在d进制下反转后的数在十进制下也是素数,就输出Yes,否则就输出No

    分析:

    判断输入是否为负数,判断n是否为素数,把n转换为d进制再反过来转换为10进制,判断是否为素数

    原文链接:https://blog.csdn.net/liuchuo/article/details/52155670

    题解

    这题重点要理解题意:
    输一个N,一个进制Radix,首先判断N是不是素数,然后先转换成Radix进制,然后倒叙,然后转换成10进制判断是不是素数。
    因为没get题意,鼓捣了半天的easy题,,,

    #include <bits/stdc++.h>
    
    using namespace std;
    bool prime(int a){
        if(a<=1) return false;
        for(int i=2;i*i<=a;i++){
            if(a%i==0) return false;
        }
        return true;
    }
    int main()
    {
    #ifdef ONLINE_JUDGE
    #else
        freopen("1.txt", "r", stdin);
    #endif
        int N,D;
        while(true){
            cin>>N;
            vector<int> v;
            if(N<0) break;
            cin>>D;
            if(!prime(N)){
                cout<<"No"<<endl;
                continue;
            }
            while(N){
                v.push_back(N%D);
                N/=D;
            }
            for(int i=0;i<v.size();i++){
                N=N*D+v[i];
            }
            if(prime(N)) cout<<"Yes"<<endl;
            else cout<<"No"<<endl;
        }
        return 0;
    }
    

    本文来自博客园,作者:勇往直前的力量,转载请注明原文链接:https://www.cnblogs.com/moonlight1999/p/15518771.html

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  • 原文地址:https://www.cnblogs.com/moonlight1999/p/15518771.html
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