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A1015. Reversible Primes (20)

1015. Reversible Primes (20)

时间限制 400 ms
内存限制 65536 kB
代码长度限制 16000 B
判题程序 Standard 作者 CHEN, Yue

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
	#include<cstdio>#include<cstring>#include<cmath>bool isPrime(int m){if(m<=1) return 0;		//必须加上这句话！int sqr = (int)(sqrt(m));for(int i = 2;i <= sqr;i++)if(m%i==0)return 0;return 1;}bool isReversible(int m,int radix){int a[16],count = 0,sum = 0;while(m){a[count++] = m%radix;m /= radix;}for(int i = 0;i < count;i++)sum = sum*radix + a[i];if(isPrime(sum)) return 1;else return 0;}int main(){int m,n;while(1){scanf("%d",&m);if(m<0) break;scanf("%d",&n);if(m!=1&&isPrime(m)&&isReversible(m,n))  printf("Yes\n");else printf("No\n");}return 0;}



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