1015. Reversible Primes (20)-PAT甲级真题

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
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

 

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