-
Notifications
You must be signed in to change notification settings - Fork 0
/
pollard_rho.cpp
72 lines (68 loc) · 1.5 KB
/
pollard_rho.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
//**********************************************
// pollard_rho 算法进行质因素分解
// 需要用到Miller-Rabin素数测试的代码
//
//*********************************************
long long factor[100];//质因素分解结果(刚返回时时无序的)
int tol;//质因素的个数,编号0~tol-1
long long gcd(long long a,long long b) {
long long t;
while(b) {
t = a;
a = b;
b = t%b;
}
if(a >= 0)return a;
else return -a;
}
//找出一个因子
long long pollard_rho(long long x,long long c) {
long long i = 1, k = 2;
srand(time(NULL));
long long x0 = rand()%(x-1) + 1;
long long y = x0;
while(1) {
i ++;
x0 = (mult_mod(x0,x0,x) + c)%x;
long long d = gcd(y - x0,x);
if( d != 1 && d != x)return d;
if(y == x0)return x;
if(i == k) {
y = x0;
k += k;
}
}
}
//对 n进行素因子分解,存入factor. k设置为107左右即可
void findfac(long long n,int k) {
if(n == 1)return;
if(Miller_Rabin(n)) {
factor[tol++] = n;
return;
}
long long p = n;
int c = k;
while( p >= n)
p = pollard_rho(p,c--);//值变化,防止死循环k
findfac(p,k);
findfac(n/p,k);
}
//POJ 1811
//给出一个N(2 <= N < 2^54),如果是素数,输出"Prime",否则输出最小的素因子
int main() {
int T;
long long n;
scanf("%d",&T);
while(T--) {
scanf("%I64d",&n);
if(Miller_Rabin(n))printf("Prime\n");
else {
tol = 0;
findfac(n,107);
long long ans = factor[0];
for(int i = 1; i < tol; i++) ans = min(ans,factor[i]);
printf("%I64d\n",ans);
}
}
return 0;
}