素数标记 Interesting Numbers URAL - 2070

Nikolay and Asya investigate integers together in their spare time. Nikolay thinks an integer is interesting if it is a prime number. However, Asya thinks an integer is interesting if the amount of its positive divisors is a
prime number (e.g., number 1 has one divisor and number 10 has four divisors).

Nikolay and Asya are happy when their tastes about some integer are common. On the other hand, they are really upset when their tastes differ. They call an integer satisfying if they both consider or do not consider this integer
to be interesting. Nikolay and Asya are going to investigate numbers from segment [ L; R] this weekend. So they ask you to calculate the number of satisfying integers from this segment.

Input

In the only line there are two integers L and R (2 ≤ L ≤ R ≤ 10 12).

Output

In the only line output one integer — the number of satisfying integers from segment [ L; R].

Example

input	output
3 7	4
2 2	1
77 1010	924

题意：在L R区间内 求的是有多少个 他的因子个数也是素数。 比如6 因子1 2 3 6 一共4个 4不是素数 就不是满足题意的。

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
using namespace std;
const int maxn = 1000000 + 10;
const int inf = 0x3f3f3f3f;
typedef long long ll;
vector<ll>prime;
int len_pri;
int vis[maxn];
void init(){
int len = sqrt(maxn) + 1;
for (int i = 2; i <= len; ++i)if (!vis[i])
for (int j = i+i; j <= maxn; j += i)vis[j] = 1; //把非素数全标记为1for (int i = 2; i <= maxn; ++i)if (!vis[i])prime.push_back(i);// 把素数全存在prime里面
len_pri = (int)prime.size();
}
int main(){
init();
ll l,r;
scanf("%I64d %I64d",&l,&r);
ll ans = 0;
for (int i = 0; i < len_pri; ++i){
ll cur = 1;
if (prime[i] * prime[i] > r)break;
int sum = 0;
while(cur < l)cur *= prime[i],++sum;//找的是非素数  从*自己开始找  因为素数一定符合条件  素数的因子是1和本身==2 2是素数
while(cur <= r){
if (sum > 1 && !vis[sum+1])++ans;
cur *= prime[i];
++sum;
}
}
printf("%I64d\n",r-l+1-ans);
return 0;
}