HUD——1286 找新朋友

Posted 2020-10-01

   

思路：

裸的欧拉函数

代码：

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
using namespace std;
int t,n,ans;
int read()
{
    int x=0,f=1; char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘) f=-1; ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘) {x=x*10+ch-‘0‘; ch=getchar();}
    return x*f;
}
int get_phi(int x)
{
    int sum=x;
    if(x%2==0)
    {
        while(x%2==0) x/=2;
        sum/=2;
    }
    for(int i=3;i*i<=x;i+=2)
    {
        if(x%i==0)
        {
           while(x%i==0) x/=i;
           sum=sum/i*(i-1);
        }
    }
    if(x>1) sum=sum/x*(x-1);
    return sum;
}
int main()
{
    t=read();
    while(t--)
    {
        n=read();
        ans=get_phi(n);
        printf("%d\\n",ans);
    }
    return  0;    
}