51nod 1135 原根

题目链接

原根相关知识：

http://blog.csdn.net/zhang20072844/article/details/11541133

——AndyZhang

（感谢原Po写得很详细）

题意：求一个质数  P 的最小原根 (P <= 1e9)

方法见上面链接

AC代码如下：

#include <bits/stdc++.h>int n, p[100010], tot;typedef long long LL;LL poww(LL a, LL b) {    LL ret = 1;    while (b) {        if (b & 1) ret = ret * a % n;        a = a * a % n;        b >>= 1;    }    return ret;}bool check(int x) {    int nn = n - 1;    for (int i = 0; i < tot; ++i) {        if (poww(x, nn / p[i]) == 1) return false;    }    return true;}void work() {    tot = 0; int nn = n - 1;    for (int i = 2; i * i <= nn; ++i) {        if (nn % i == 0) {            p[tot++] = i;            while (nn % i == 0) nn /= i;        }    }    if (nn > 1) p[tot++] = nn;    for (int i = 1; i < n; ++i) {        if (check(i)) { printf("%d\n", i); return; }    }}int main() {    while (scanf("%d", &n) != EOF) work();    return 0;}