标签：put -- case nsis tst prime htm you lse
https://pintia.cn/problem-sets/994805342720868352/problems/994805495863296000
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 (<) and D (1), you are supposed to tell if N is a reversible prime with radix D.
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.
For each test case, print in one line Yes if N is a reversible prime with radix D, or No if not.
73 10
23 2
23 10
-2
Yes
Yes
No
时间复杂度：$ O(\sqrt{N}) $
代码：
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
int prime(int x) {
if(x == 1) return 0;
if(x == 2) return true;
for(int i = 2; i * i <= x; i ++)
if(x % i == 0)
return 0;
return 1;
}
int main() {
int N, D;
int num[maxn];
while(~scanf("%d", &N)) {
if(!N) break;
scanf("%d", &D);
if(prime(N) == 0) {
printf("No\n");
continue;
}
else {
int cnt = 0;
do{
num[cnt ++] = N % D;
N /= D;
}while(N);
int sum = 0, k = 0;
for(int i = cnt - 1; i >= 0; i --) {
sum += num[i] * pow(D, k);
k ++;
}
if(prime(sum))
printf("Yes\n");
else
printf("No\n");
}
}
return 0;
}
标签：put -- case nsis tst prime htm you lse
原文地址：https://www.cnblogs.com/zlrrrr/p/9670932.html
