题目链接
(BSGS)模板题。。不会点这里
#include <cstdio>
#include <cmath>
#include <map>
using namespace std;
typedef long long ll;
int a, b, p;
int fast_pow(int n, int k){ //n^k%p
int ans = 1;
while(k){
if(k & 1) ans = (ll)ans * n % p;
n = (ll)n * n % p;
k >>= 1;
}
return ans;
}
int BSGS(){ //a^x≡b(mod p)
map <int, int> hash; hash.clear();
int t = ceil(sqrt(p)), val = b, j = 1;
for(int i = 0; i < t; ++i){
hash[val] = i;
val = (ll)val * a % p;
}
a = fast_pow(a, t);
if(!a) return !b ? 1 : -1;
for(int i = 0; i <= t; ++i){
int k = hash.find(j) == hash.end() ? -1 : hash[j];
if(k >= 0 && (i * t - k) >= 0) return i * t - k;
j = (ll)j * a % p;
}
return -1;
}
int main(){
scanf("%d%d%d", &p, &a, &b);
int ans = BSGS();
if(ans == -1) printf("no solution
");
else printf("%d
", ans);
return 0;
}