POJ 3292

Semi-prime H-numbers

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 7059		Accepted: 3030

Description

This problem is based on an exercise of David Hilbert, who pedagogically suggested that one study the theory of 4n+1 numbers. Here, we do only a bit of that.

An H-number is a positive number which is one more than a multiple of four: 1, 5, 9, 13, 17, 21,... are the H-numbers. For this problem we pretend that these are the only numbers. The H-numbers are closed under multiplication.

As with regular integers, we partition the H-numbers into units, H-primes, and H-composites. 1 is the only unit. An H-number h is H-prime if it is not the unit, and is the product of two H-numbers in only one way: 1 × h. The rest of the numbers are H-composite.

For examples, the first few H-composites are: 5 × 5 = 25, 5 × 9 = 45, 5 × 13 = 65, 9 × 9 = 81, 5 × 17 = 85.

Your task is to count the number of H-semi-primes. An H-semi-prime is an H-number which is the product of exactly two H-primes. The two H-primes may be equal or different. In the example above, all five numbers are H-semi-primes. 125 = 5 × 5 × 5 is not an H-semi-prime, because it's the product of three H-primes.

Input

Each line of input contains an H-number ≤ 1,000,001. The last line of input contains 0 and this line should not be processed.

Output

For each inputted H-number h, print a line stating h and the number of H-semi-primes between 1 and h inclusive, separated by one space in the format shown in the sample.

Sample Input

21
85
789
0

Sample Output

21 0
85 5
789 62

Source

Waterloo Local Contest, 2006.9.30

 

 

仿照素数的埃氏筛选法即可

 

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <iostream>

 using namespace std;

 #define maxn 1000005

 bool H[maxn];
 int ans[maxn],ele[maxn];
 int len = ;

 void init() {

         for(int i = ; i <= maxn - ; i++) {
                 H[i] = (i %  == );
         }

         for(int i = ; i * i <= maxn - ; i += ) {
                 if(!H[i]) continue;
                 for(int j = i; j * i <= maxn - ; j++) {
                         H[j * i] = ;
                 }
         }

         for(int i = ; i <= maxn - ; i += ) {
                 if(H[i]) {
                         ele[len++] = i;
                 }
         }

         for(int i = ; i < len && ele[i] * ele[i] <= maxn - ; i++) {
                 for(int j = i; j < len && ele[j] * ele[i] <= maxn - ; j++) {
                         if(ele[i] * ele[j] %  == )
                         ans[ ele[i] * ele[j] ] = ;
                 }
         }

         for(int i = ; i <=  maxn - ; i++) {
                 ans[i] += ans[i - ];
         }
 }

 int main() {
        // freopen("sw.in","r",stdin);

         init();

         int x;
         while(~scanf("%d",&x) && x) {
                 printf("%d %d\n",x,ans[x]);
         }

         return ;

 }