UVA - 10006 Carmichael Numbers

题意：判断是否对于所有情况都成立，用到了打素数表和幂取模，LRJ上都有详细的代码

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
const int MAXN = 65005;

bool vis[MAXN];

void isPrime(int n){
    memset(vis,false,sizeof(vis));
    int m = sqrt(n+0.5);
    for (int i = 2; i <= m; i++)
        if (!vis[i]){
            for (int j = i * i; j <= n; j += i)
                vis[j] = true;
        }
}

int pow_mod(int a,int n,int num){
    if (n == 1)
        return a;
    int x = pow_mod(a,n/2,num);
    long long ans = (long long) x * x % num;
    if (n % 2 == 1)
        ans = (ans * a) % num;
    return (int)ans;
}

bool judge(int num){
    int ans;
    for (int i = 2; i < num; i++){
        ans = pow_mod(i,num,num);
        if (ans != i)
            return false;
    }
    return true;
}

int main(){
    int num;
    isPrime(MAXN);
    while (scanf("%d",&num) != EOF && num){
        if (vis[num] && judge(num))
            printf("The number %d is a Carmichael number.\n", num);  
        else  
            printf("%d is normal.\n", num);
    }
    return 0;
}