uva 10006 - Carmichael Numbers

考同余跟快速幂取模

#include <stdio.h>#include <string.h>#define MAX 65001bool isPrimer[MAX];//筛选法求素数void init() {memset(isPrimer, true, sizeof(isPrimer));isPrimer[0] = isPrimer[1] = false;for(int i = 2; i * i <= MAX; i++) {if(isPrimer[i])for(int j = i * i; j <= MAX; j += i)isPrimer[j] = false;}}//快速幂取模long mod(long a, long n, long m) {if(n == 1) return a % m;long ans = mod(a, n >> 1, m);ans = ans * ans % m;if(n % 2 == 1) return ans * a % m;return ans;}bool check(long n) {for(long a = 2; a < n; a++)if(mod(a, n, n) != a) return false;return true;}int main() {init();long n;while(~scanf("%ld", &n) && n != 0) {if(!isPrimer[n] && check(n))printf("The number %ld is a Carmichael number./n",n); else printf("%ld is normal./n",n);}return 0;}