uva 11408 Count DePrimes求素数変式
4602 ワード
A number is called a DePrime if the sum of its prime factors is a prime number. Given a and b count the number of DePrimes xi such that a ≤ xi ≤ b. Input Each line contains a and b in the format ‘a b’. 2 ≤ a ≤ 5000000. a ≤ b ≤ 5000000. Input is terminated by a line containing ‘0’. Output Each line should contain the number of DePrimes for the corresponding test case. Explanation: In Test Case 2, take 10. Its Prime Factors are 2 and 5. Sum of Prime Factors is 7, which is a prime. So, 10 is a DePrime.
Sample Input 2 5 10 21 100 120 0 Sample Output 4 9 9
a,bを与えて、a-bの間の質の因子と質の数の個数の構想を求めます:素の数を求めて表を打つ同時に各数の質の因子と
素数を求めて表を打つ:
acコード:
Sample Input 2 5 10 21 100 120 0 Sample Output 4 9 9
a,bを与えて、a-bの間の質の因子と質の数の個数の構想を求めます:素の数を求めて表を打つ同時に各数の質の因子と
素数を求めて表を打つ:
void init()
{
int num=1;
memset(prime,0,sizeof(prime));
memset(visit,false,sizeof(visit));
for(int i=2;i//
{
if(!visit[i])
prime[num++]=i;
for(int j=1;j<=num&&i*prime[j]true;
if(i%prime[j]==0)
break;
}
}
visit[1]=true;
}
acコード:
#include
#include
using namespace std;
const int Maxn=5000005;
int prime[Maxn];
bool mark[Maxn];
int n[Maxn];
int sum[Maxn];// i
void init()
{
int i,j,num=1;
n[0]=0;
n[1]=0;
memset(prime,0,sizeof(prime));
memset(mark,true,sizeof(mark));
for(i=2;iif(mark[i])
{
prime[num++]=i;
sum[i]=i;
}
for(j=1;jif(i*prime[j]>Maxn)
break;
mark[i*prime[j]]=false;
if(i%prime[j]==0)
{
sum[i*prime[j]]=sum[i];
break;
}
sum[i*prime[j]]=sum[i]+prime[j];
}
if(mark[sum[i]])
n[i]=n[i-1]+1;
else
n[i]=n[i-1];
}
}
int main()
{
int a,b;
init();
while(cin>>a)
{
if(a==0)
break;
cin>>b;
cout<1]<return 0;
}