Almost prime numbers are the non-prime numbers which are divisible by only a single prime number. In this problem your job is to write a program which finds out the number of almost prime numbers within a certain range.
Input
First line of the input file contains an integer N (N ≤ 600) which indicates how many sets of inputs are there. Each of the next N lines make a single set of input. Each set contains two integer numbers low and high (0 < low ≤ high < 1012).
Output
For each line of input except the first line you should produce one line of output. This line contains a single integer, which indicates how many almost prime numbers are within the range (inclusive) low…high.
Sample Input
3
1 10 1 20 15
Sample Output
3 4 1
題意:
給出範圍low~high,問說在這個範圍內有多少個數滿足n=p^b(p爲素數)
思路:
首先打表處理出1e6以內的素數,然後循環素數表中
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <cstring>
using namespace std;
long long prime[1000001];
int j[1000001];
int cnt=0;
void tab()
{
int max=1000001;
for(int i=2;i<max;i++)
{
if(j[i]==0)
{
prime[cnt++]=i;
for(int k=i*2;k<max;k+=i)
j[k]=1;
}
}
}
int main()
{
tab();
int N,i,sum;
long long low,high,m;
cin>>N;
while(N--)
{
sum=0;
cin>>low>>high;
for(i=0;i<cnt;i++)
{
m=prime[i]*prime[i];
if(m>high)
break;
while(m<=high)
{
if(m>=low)
sum++;
m*=prime[i];
}
}
cout<<sum<<endl;
}
return 0;
}