Java求歐拉函數 (n)_數論之求歐拉函數

簡單的求歐拉函數的值，留下來做個模闆。。。。。。。。。。

題目：

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

Sample Output

6

4

ac代碼：

#include

#include

#include

using namespace std;

long long euler(long long y){

int m=(int)sqrt(y+0.5);

int ans=y;

for(int i=2;i<=m;++i){

if(y%i==0){

ans=ans/i*(i-1);

while(y%i==0)

y/=i;

}

}

if(y>1)

ans=ans/y*(y-1);

return ans;

}

int main()

{

long long n;

while(cin>>n&&n){

long long x=euler(n);

cout<

}

}