POJ3243 Clever Y "Higher secondary congruence equation"

Topic Links:

http://poj.org/problem?id=3243

Main topic:

known formula A^x mod C = B , and the value of a, C, B to solve the value of x.

Ideas:

The typical solution equation a^x = B (mod C), the direct template solves.

AC Code:

#include <iostream> #include <algorithm> #include <cstdio> #include <cstring> #include <    Cmath> #define LL __int64using namespace Std;const int maxn = 65535;struct hash{int A;    int b; int next;}    Hash[maxn*2];int flag[maxn+66];int top,idx;void ins (int a,int b) {int k = b & maxn;        if (flag[k]! = IDX) {Flag[k] = idx;        Hash[k].next =-1;        HASH[K].A = A;        hash[k].b = b;    Return        } while (Hash[k].next! =-1) {if (hash[k].b = = b) return;    K = Hash[k].next;    } hash[k].next = ++top;    Hash[top].next =-1;    HASH[TOP].A = A; hash[top].b = b;}    int Find (int b) {int k = b & maxn;    if (flag[k]! = idx) return-1;        while (k! =-1) {if (hash[k].b = = b) return hash[k].a;    K = Hash[k].next; } return-1;}    int GCD (int a,int b) {if (b = = 0) return A; Return GCD (b,a%b);}    int exgcd (int a,int b,int &x,int &y) {int temp,ret; if (!b) {x = 1;        y = 0;    return A;    } ret = EXGCD (b,a%b,x,y);    temp = x;    x = y;    y = temp-a/b*y; return ret;}    int inval (int a,int b,int n) {int x,y,e;    EXGCD (A,n,x,y);    E = (LL) x*b%n; Return e < 0? e + n:e;}    int Powmod (ll a,int b,int c) {ll ret = 1%c;    a%= C;        while (b) {if (b&1) ret = ret*a%c;        A = a*a%c;    b >>= 1; } return ret;}    int babystep (int a,int b,int C) {top = MAXN;    ++idx;    LL buf = 1%c,d = Buf,k;    int d = 0,temp,i;    for (i = 0; I <=; buf = buf*a%c,++i) {if (buf = = B) return i;        } while ((temp = GCD (a,c)) = 1) {if (B temp) return-1;        ++d;        C/= temp;        B/= temp;    D = d*a/temp%c;    } int M = (int) ceil (sqrt ((double) C));    for (buf = 1%c,i = 0; I <= M; buf = buf*a%c,++i) ins (i,buf); for (i = 0,k = Powmod (LL) a,m,c); I <= M; D = d*k%c,++i) {temp = inval ((int) d, b,c);        int W;    if (temp >= 0 && (w = Find (temp))! =-1) return I * M + W + D; } return-1;}    int main () {int a,b,c; while (~SCANF ("%d%d%d", &a,&c,&b) && (a| | b| |        c)) {B%= C;        int temp = Babystep (a,b,c);        if (Temp < 0) printf ("No solution\n");    else printf ("%d\n", temp); } return 0;}

POJ3243 Clever Y "Higher secondary congruence equation"