1 Accepted 406MS 8576K 2379 B C++/**
2 这里加了一点限制，，大体还是一样的，，
3
4 **/
5 #include <iostream>
6 #include <cstdio>
7 #include <cmath>
8 #include <cstring>
9 #include <algorithm>
10 using namespace std;
11 long long a,b,n;
12 const int maxn = 499991;
13 bool Hash[maxn];
14 long long val[maxn];
15 long long idx[maxn];
16
17 long long gcd(long long a,long long b){
18 if(b==0)
19 return a;
20 return gcd(b,a%b);
21 }
22
23 void ex_gcd(long long a,long long b,long long &x,long long &y){
24 if(b==0){
25 x=1;
26 y=0;
27 return ;
28 }
29 ex_gcd(b,a%b,x,y);
30 long long tmp= x-(a/b)*y;
31 x = y;
32 y = tmp;
33 return ;
34 }
35
36 void Insert(long long id,long long num){
37 long long k = num%maxn;
38 while(Hash[k]&&val[k]!=num){
39 k++;
40 if(k==maxn) k = k-maxn;
41 }
42 if(!Hash[k]){
43 Hash[k] = true;
44 val[k] = num;
45 idx[k] = id;
46 }
47 return;
48 }
49
50 long long found(long long num){
51 long long k = num%maxn;
52 while(Hash[k]&&val[k]!=num){
53 k++;
54 if(k==maxn) k-=maxn;
55 }
56 if(Hash[k]){
57 return idx[k];
58 }
59 return -1;
60 }
61
62 long long baby_step(long long a,long long b,long long n){
63 long long temp =1;
64 long long i;
65 for(i=0;i<=100;i++){
66 if(temp==b%n) return i;
67 temp = temp*a%n;
68 }
69 long long tmp,d =1,cnt=0;
70 memset(Hash,false,sizeof(Hash));
71 memset(val,-1,sizeof(val));
72 memset(idx,-1,sizeof(idx));
73
74 while((tmp=gcd(a,n))!=1){
75 if(b%tmp)
76 return -1;
77 cnt++;
78 n = n/tmp;
79 b = b/tmp;
80 d =d*a/tmp%n;
81 }
82 long long cur =1;
83 long long m = ceil(sqrt(n+0.5));
84 for(i=0;i<m;i++){
85 Insert(i,cur);
86 cur = cur*a%n;
87 }
88 long long x,y;
89 for(i=0;i<m;i++){
90 ex_gcd(d,n,x,y);
91 x = x*b%n;
92 x = (x%n+n)%n;
93 long long k = found(x);
94 if(k!=-1)
95 return i*m+k+cnt;
96 d = d*cur%n;
97 }
98 return -1;
99 }
100
101 int main()
102 {
103 while(scanf("%I64d%I64d%I64d",&a,&n,&b)==3){
104 if(b>=n){
105 printf("Orz,I can’t find D!\n");
106 continue;
107 }
108 if(n==1){
109 printf("0\n");
110 continue;
111 }
112 long long res = baby_step(a,b,n);
113 if(res==-1){
114 printf("Orz,I can’t find D!\n");
115 }else{
116 printf("%I64d\n",res);
117 }
118 }
119 return 0;
120 }
hdu 2815 Mod Tree 高次方程，n不为素数
时间： 2024-08-01 16:54:31