POJ2407(欧拉函数)

Relatives

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 13598		Accepted: 6771

Description

Given n, a positive integer, how many positive integers less than n are relatively prime to n? Two integers a and b are relatively prime if there are no integers x > 1, y > 0, z > 0 such that a = xy and b = xz.

Input

There are several test cases. For each test case, standard input contains a line with n <= 1,000,000,000. A line containing 0 follows the last case.

Output

For each test case there should be single line of output answering the question posed above.

Sample Input

7
12
0

Sample Output

6
4

裸的欧拉函数，因为n的数据比较大，不用筛选法打欧拉函数表，直接用公式：

　　

 //2016.8.17
 #include<iostream>
 #include<cstdio>

 using namespace std;

 int phi(int n)
 {
     int ans = n;
     for(int i = ; i <= n; i++)
     {
         if(n%i==)
         {
             ans -= ans/i;
             while(n%i==)
                 n /= i;
         }
         if(n == )break;
     }
     return ans;
 }

 int main()
 {
     int n;
     while(cin>>n&&n)
     {
         cout<<phi(n)<<endl;
     }

     return ;
 }