hdu 4279 Number

http://acm.hdu.edu.cn/showproblem.php?pid=4279

Problem Description

　　Here are two numbers A and B (0 < A <= B). If B cannot be divisible by A, and A and B are not co-prime numbers, we define A as a special number of B.
　　For each x, f(x) equals to the amount of x’s special numbers.
　　For example, f(6)=1, because 6 only have one special number which is 4. And f(12)=3, its special numbers are 8,9,10.
　　When f(x) is odd, we consider x as a real number.
　　Now given 2 integers x and y, your job is to calculate how many real numbers are between them.

 

Input

　　In the first line there is an integer T (T <= 2000), indicates the number of test cases. Then T line follows, each line contains two integers x and y (1 <= x <= y <= 2^63-1) separated by a single space.

 

Output

　　Output the total number of real numbers.

 

Sample Input

2 1 1 1 10

 

Sample Output

0 4

Hint

For the second case, the real numbers are 6,8,9,10.

 

 

这题实在是规律难找，参考了几位大神的代码

代码（1）：参考自http://www.cnblogs.com/yejinru/archive/2012/09/09/2677747.html

#include <cstdio>
 #include <cmath>
 #include <cstring>
 #include <algorithm>
 #include <iostream>
 
 using namespace std;
 
 long long a, b, t;
 long long s1, s2;
 
 int main()
 {
      int T;
      scanf("%d", &T);
      while(T--) {
           cin>>a>>b;
           --a;
           s1 = a >> 1;
           s2 = b >> 1;
 
           t = sqrt(a);
           s1 -= t >> 1;
           s1 += t-(t>>1);
 
           t = sqrt(b);
           s2 -= t >> 1;
           s2 += t-(t>>1);
 
           if (a >= 1) s1 -= 1;
           if (a >= 2) s1 -= 1;
           if (b >= 1) s2 -= 1;
           if (b >= 2) s2 -= 1;
           s2 -= s1;
           cout<<s2<<endl;
      }
      return 0;
 }

代码（2）：参考自http://blog.csdn.net/kk303/article/details/7960986

#include<iostream>
#include<cmath>
using namespace std;      
int t,n,s[20]={0,0,0,0,0,0,1,1,2,3,4,4,5};   
__int64 a,b,p1,p2;
__int64 getsum(__int64 x)
{
     if (x<=12) return s[x];
     __int64 m,k;
     m=x/2; 
     k=(__int64)sqrt(x);
     if (k%2==0) m-=2;
        else m-=1;
     return m;
}
int main()
{  
    // freopen("input.txt","r",stdin);    freopen("output.txt","w",stdout); 
     scanf("%d",&t);
     while (t--)
     { 
            scanf("%I64d%I64d",&a,&b);
            a--;
            p1=getsum(a);  
            p2=getsum(b);
            printf("%I64d\n",p2-p1);
     }
     return 0;
}