POJ 1811 Prime Test (Miller-Robin+Pollard_rho)

题意

判断一个大数是不是素数，如果不是输出最小的质因子。

思路

Miller-Robin+Pollard_rho，算是这两个算法的模板题吧。
感觉随机挺玄学的。。。
要注意在找质因子的时候，gcd那里y-x0有可能是负的，因为这个疯狂TLE

代码

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>using namespace std;#define LL long long#define Lowbit(x) ((x)&(-x))#define lson l, mid, rt << 1#define rson mid + 1, r, rt << 1|1#define MP(a, b) make_pair(a, b)const int INF = 0x3f3f3f3f;const int MOD = 1000000007;const int maxn = 1e5 + 10;const double eps = 1e-8;const double PI = acos(-1.0);typedef pair<int, int> pii;const int S = 20;LL q_mul(LL a, LL b, LL p){    a %= p;    b %= p;    LL res = 0;    while (b)    {        if (b & 1) res = (res + a) % p;        a <<= 1;        if (a >= p) a %= p;        b >>= 1;    }    return res;}LL q_pow(LL x, LL n, LL mod){    LL temp = x;    LL res = 1;    while (n)    {        if (n & 1) res = q_mul(res, temp, mod);        temp = q_mul(temp, temp, mod);        n >>= 1;    }    return res;}//判断是不是一定是合数bool check(LL a, LL n, LL x, LL t){    LL res = q_pow(a, x, n);    LL last = res;    for (int i = 1; i <= t; i++)    {        res = q_mul(res, res, n);        if (res == 1 && last != 1 && last != n - 1)  //二次检测            return 1;        last = res;    }    if (res != 1) return 1;    return 0;}bool Miller_Rabin(LL n){    if (n < 2) return 0;    if (n == 2) return 1;    if (!(n & 1)) return 0;    LL x = n - 1;    LL t = 0;    while ((x & 1) == 0)        x >>= 1, t++;    for (int i = 0; i < S; i++)    {        LL a = rand() % (n - 1) + 1;        if (check(a, n, x, t))            return 0;            //合数    }    return 1;                    //伪素数}LL factor[110];                   //无序质因子int tot;LL Pollard_rho(LL x, LL c){    LL i = 1, k = 2;    LL x0 = rand() % x;    LL y = x0;    while (1)    {        i++;        x0 = (q_mul(x0, x0, x) + c) % x;        LL d = __gcd(y - x0 + x, x);      //注意负数！        if (d != 1 && d != x) return d;        if (y == x0) return x;        if (i == k) { y = x0; k += k;}    }}void findfac(LL n){    if (Miller_Rabin(n))    {        factor[tot++] = n;        return ;    }    LL p = n;    while (p >= n)        p = Pollard_rho(p, rand() % (n - 1) + 1);    findfac(p);    findfac(n / p);}int main(){    //freopen("in.txt","r",stdin);    //freopen("out.txt","w",stdout);    int T;    scanf("%d", &T);    while (T--)    {        LL n;        scanf("%lld", &n);        if (Miller_Rabin(n))            puts("Prime");        else        {            tot = 0;            findfac(n);            LL ans = factor[0];            for (int i = 1; i < tot; i++)                ans = min(ans, factor[i]);            printf("%lld\n", ans);        }    }    return 0;}