1.题目
Give you a prime number p, if you could find some natural number (0 is not inclusive) n and m, satisfy the following expression:
We call this p a “Special Prime”.
AekdyCoin want you to tell him the number of the “Special Prime” that no larger than L.
For example:
If L =20
1^3 + 71^2 = 2^3
8^3 + 198^2 = 12^3
That is to say the prime number 7, 19 are two “Special Primes”.
Input
The input consists of several test cases.
Every case has only one integer indicating L.(1<=L<=10^6)
Output
For each case, you should output a single line indicate the number of “Special Prime” that no larger than L. If you can’t find such “Special Prime”, just output “No Special Prime!”
Sample Input
7
777
Sample Output
1
10
2.代码
#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
const int maxn=1e6+10;
int prime[maxn],ans[maxn];
void isprime()
{
prime[0]=1;
prime[1]=1;
for(int i=2;i<maxn;i++)
{
if(prime[i]==0)
{
for(int j=i+i;j<maxn;j+=i)
prime[j]=1;
}
}
}
bool judge(int p)//判断12*P-3是否是平方数
{
int m=12*p-3;
int k=(int)sqrt(m);
return k*k==m;
}
void table()
{
for(int i=1;i<maxn;i++)
{
if(!prime[i]&&judge(i))
ans[i]++;
ans[i]+=ans[i-1];
}
}
int main()
{
isprime();
table();
int l;
while(cin>>l)
{
if(ans[l])
cout<<ans[l]<<endl;
else
cout<<"No Special Prime!"<<endl;
}
return 0;
}