Reversible Primes (20)stoi应用

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 1023 223 10-2

Sample Output:

YesYesNo

int stoi (const string&  str, size_t* idx = 0, int base = 10);//将字符转化为整形
int stol (const string&  str, size_t* idx = 0, int base = 10);//将字符转化为long
int stoul (const string&  str, size_t* idx = 0, int base = 10);//将字符转化为unsigned long
int stoll (const string&  str, size_t* idx = 0, int base = 10);//将字符转化为long long
int stoull (const string&  str, size_t* idx = 0, int base = 10);//将字符转化为unsigned long long

str表示原始字符串，idx表示s中第一个非字符数值下标，默认为0，若字符中都是数字应该输入nullptr，base是转换所用基数默认为10

例如str=“110” 用stoi（str，nullptr，2） 就转化为了整数6

题意：

给定一个数N，给定一个基数D若N为素数并且将N转化为D进制后反向N’，也为素数

例如23 2

23为素数，将23转化为2进制为10111，反向后为11101是29也为素数所以输出Yes

#include<iostream>#include<string>using namespace std;bool isprime(int n)//判断素数{if(n<2)return false;for(int i=2;i<=n/2;i++)if(n%i==0)return false;return true;}int reverse(int n,int radix)//按进制反向{string s;while(n>0)//求反向radix进制数{s.push_back(n%radix+'0');n/=radix;}return stoi(s,nullptr,radix);}int main(){int n,radix;while(cin>>n&&n>= 0){cin>>radix;if(isprime(n)&&isprime(reverse(n,radix)))cout<<"Yes"<<endl;elsecout<<"No"<<endl;}return 0;}