求原根

 输入m, 输出它的所有原根

 Code：

#include<bits/stdc++.h>
using namespace std;

int ele[100000];
bool IsPrime(int num)
{
    bool flag = true;
    for(int i = 2; i <= sqrt(num); i++)
    {
        if(num % i == 0) {
            flag = false;
            while(num % i == 0){
                ele[i]++;
                num /= i;
            }
        }
    }
    return flag;
}

int Euler(int num)
{
    if(IsPrime(num))
        return num-1;
    else
    {
        int ans = num;
        for(int i = 0; i <= sqrt(num); i++)
        {
            if(ele[i] != 0)
                ans = (ans/i) * (i-1);
        }
        return ans;
    }

}

int Pow(int a, int b, int mod)
{
    int ans = 1, base = a%mod;
    while(b != 0)
    {
        if(b & 1)
            ans = (ans * base) % mod;
        base = (base * base) % mod;
        b >>= 1;
    }
    return ans;
}

int main()
{
    int m;
    while(scanf("%d", &m) != EOF)
    {
        int i, j;
        int ans = Euler(m);
        for(i = 1; i < m; i++)
        {
            for(j = 1; j <= ans; j++)
                if(Pow(i, j, m) == 1)
                    break;
            if(j == ans)
                cout << i << endl;
        }
    }
    return 0;
}