BSGS模板 

 1 #include<cmath>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #define mod 600000
 6 using namespace std;
 7 int cnt;
 8 long long a,b,c;
 9 int head[600005];
10 struct Edge{
11     int fr;
12     int val;
13     int nxt;
14     long long to;
15 }edge[600005];
16 void addedge(int u,long long v,int w){
17     edge[cnt].fr=u;
18     edge[cnt].to=v;
19     edge[cnt].val=w;
20     edge[cnt].nxt=head[u];
21     head[u]=cnt++;
22 }
23 void init(){
24     cnt=0;
25     memset(head,-1,sizeof(head));
26 }
27 long long BSGS(long long A,long long B,long long C){
28     init();
29     int m=sqrt(C);
30     long long mul1=1;
31     long long mul2=1;
32     for(int i=1;i<=m;i++){
33         mul1=(mul1*A)%C;
34         long long ad=(mul1*B)%C;
35         if(!ad)return -1;
36         addedge(ad%mod,ad,i);
37     }
38     for(int i=1;i<=m+3;i++){
39         mul2=(mul2*mul1)%C;
40         for(int j=head[mul2%mod];j!=-1;j=edge[j].nxt){
41             long long v=edge[j].to;
42             if(v==mul2)return 1ll*i*m-edge[j].val;
43         }
44     }
45     return -1;
46 }
47 int main(){
48     scanf("%lld%lld%lld",&c,&a,&b);
49     long long ans=BSGS(a,b,c);
50     if(ans==-1)printf("no solution\n");
51     else printf("%lld\n",ans);
52     return 0;
53 }

 

posted @ 2019-01-04 15:49  Mr_Handsome  阅读(251)  评论(0)    收藏  举报