1 const int S = 20;//随机算法判定次数，S越大，判错概率越小
2 LL pow_mod(LL a, LL b, LL mod) { // a^b%mod
3 LL ans = 1;
4 a = a % mod;
5 while(b) {
6 if(b & 1) {
7 ans = (ans * a) % mod;
8 }
9 a = ( a * a ) % mod;
10 b >>= 1;
11 }
12 return ans;
13 }
14 bool check(LL a, LL n, LL x, LL t) {
15 LL ret = pow_mod(a, x, n);
16 LL last = ret;
17 for(int i = 1; i <= t; i++) {
18 ret = (ret * ret) % n;
19 if(ret == 1 && last != 1 && last != n - 1) return true;
20 last = ret;
21 }
22 if(ret != 1) return true;
23 else return false;
24 }
25 bool Miller_Rabin(long long n) {
26 if(n < 2)return false;
27 if(n == 2) return true;
28 if( (n & 1) == 0) return false;
29 LL x = n - 1;
30 LL t = 0;
31 while( (x & 1) == 0 ) {
32 x >>= 1;
33 t++;
34 }
35 for(int i = 0; i < S; i++) {
36 LL a = rand() % (n - 1) + 1;
37 if(check(a, n, x, t))
38 return false;
39 }
40 return true;
41 }
