POJ 2407 Relatives 欧拉函数

水题

euler 是直接判断 

euler2 是欧拉筛

/********************* Template ************************/
#include <set>
#include <map>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <string>
#include <vector>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <fstream>
#include <numeric>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;

#define EPS         1e-8
#define MAXN        1005
#define MOD         (int)1e9+7
#define PI          acos(-1.0)
#define DINF        (1e10)
#define LINF        ((1LL)<<50)
#define INF         (0x3f3f3f3f)
#define max(a,b)    ((a) > (b) ? (a) : (b))
#define min(a,b)    ((a) < (b) ? (a) : (b))
#define max3(a,b,c) (max(max(a,b),c))
#define min3(a,b,c) (min(min(a,b),c))
#define BUG         cout<<"BUG! "<<endl
#define line        cout<<"--------------"<<endl
#define L(t)        (t << 1)
#define R(t)        (t << 1 | 1)
#define Mid(a,b)    ((a + b) >> 1)
#define lowbit(a)   (a & -a)
#define FIN         freopen("in.txt","r",stdin)
#define FOUT        freopen("out.txt","w",stdout)
#pragma comment     (linker,"/STACK:102400000,102400000")

// typedef long long LL;
// typedef unsigned long long ULL;
typedef __int64 LL;
// typedef unisigned __int64 ULL;
// LL gcd(LL a,LL b){ return b?gcd(b,a%b):a; }
// LL lcm(LL a,LL b){ return a*b/gcd(a,b); }

/*********************   F   ************************/
int euler(LL n){
    int x = n;
    int phi = n;
    for(int i = 2 ; i*i <= n ; i++){
        if(x % i == 0){
            phi = phi / i * (i-1);
            while(x % i == 0) x /= i;
        }
    }
    if(x != 1) phi = phi / x * (x-1);
    return phi;
}
int phi[100001];
void euler2()
{
    phi[1] = 1;
    for(int i = 2; i <= 100000; i++){
        if(!phi[i]){
            for(int j = i; j <= 100000; j += i){
                if(!phi[j]) phi[j] = j;
                phi[j] = phi[j] / i * (i - 1);
            }
        }
    }
}
int main()
{
    //FIN;
    //FOUT;
    LL n;
    while(~scanf("%I64d",&n) && n){
        printf("%d\n",euler(n));
    }
    return 0;
}