Red Huang

Red Huang

uva 10956

First learned such a fast method to determine prime numbers

This is the Fermat test; as long as it is determined that these three bases {2,7,61} are all true

It can correctly determine that numbers below 2^32 are prime

The complexity is O(logN)

//  
//        GGGGGGGGGGGGG        CCCCCCCCCCCCC               AAA  
//     GGG::::::::::::G     CCC::::::::::::C              A:::A  
//   GG:::::::::::::::G   CC:::::::::::::::C             A:::::A  
//  G:::::GGGGGGGG::::G  C:::::CCCCCCCC::::C            A:::::::A  
// G:::::G       GGGGGG C:::::C       CCCCCC           A:::::::::A  
//G:::::G              C:::::C                        A:::::A:::::A  
//G:::::G              C:::::C                       A:::::A A:::::A  
//G:::::G    GGGGGGGGGGC:::::C                      A:::::A   A:::::A  
//G:::::G    G::::::::GC:::::C                     A:::::A     A:::::A  
//G:::::G    GGGGG::::GC:::::C                    A:::::AAAAAAAAA:::::A  
//G:::::G        G::::GC:::::C                   A:::::::::::::::::::::A  
// G:::::G       G::::G C:::::C       CCCCCC    A:::::AAAAAAAAAAAAA:::::A  
//  G:::::GGGGGGGG::::G  C:::::CCCCCCCC::::C   A:::::A             A:::::A  
//   GG:::::::::::::::G   CC:::::::::::::::C  A:::::A               A:::::A  
//     GGG::::::GGG:::G     CCC::::::::::::C A:::::A                 A:::::A  
//        GGGGGG   GGGG        CCCCCCCCCCCCCAAAAAAA                   AAAAAAA  
#include <iostream>  
#include <cstdio>  
#include <cstring>  
#include <algorithm>  
#include <cmath>  
#include <climits>  
#include <vector>  
#include <set>  
#include <map>  
#include <queue>  
#include <cctype>  
#include <utility>  
#include <ctime>  
using namespace std;  
#ifdef DEBUG  
#define VAR(a,b) decltype(b) a=(b)  
#define debug(...) printf("DEBUG: "),printf(__VA_ARGS__)  
#define gettime() end_time=clock();printf("now running time is %.7f\\n",(float)(end_time - start_time)/CLOCKS_PER_SEC);  
#else  
#define VAR(a,b) __typeof(b) a=(b)  
#define debug(...)  
#define gettime()  
#endif  
typedef unsigned int uint;  
typedef unsigned long long int Int;  
#define Set(a,s) memset(a,s,sizeof(a))  
#define Write(w) freopen(w,"w",stdout)  
#define Read(r) freopen(r,"r",stdin)  
#define Pln() printf("\\n")  
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()  
#define De(x)printf(#x"%d\\n",x)  
#define For(i,x)for(int i=0;i<x;i++)  
#define CON(x,y) x##y  
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\\  
    printf("%d ",dp[htx][hty]);}Pln();}  
#define M 55  
#define PII pair<int,int>  
#define PB push_back  
#define oo INT_MAX  
#define Set_oo 0x3f  
#define FOR(a,b) for(VAR(a,(b).begin());a!=(b).end();++a)  
#define eps 1e-6  
clock_t start_time=clock(), end_time;  
bool xdy(double x,double y){return x>y+eps;}  
bool xddy(double x,double y){return x>y-eps;}  
bool xcy(double x,double y){return x<y-eps;}  
bool xcdy(double x,double y){return x<y+eps;}  
int min3(int x,int y,int z){  
    int tmp=min(x,y);  
    return min(tmp,z);  
}  
int max3(int x,int y,int z){  
    int tmp=max(x,y);  
    return max(tmp,z);  
}  
Int powmod(Int b,Int u,Int n){  
    Int ans=1;  
    Int base=b;  
    while(u){  
        if(u&1)  
            ans=ans*base%n;  
        base=base*base%n;  
        u>>=1;  
    }  
    return ans;  
}  
bool suspect(Int b,Int n){  
    Int exp=0;  
    Int t=n-1;  
    while(!(t&1)){  
        exp++;  
        t>>=1;  
    }  
    Int xi=powmod(b,t,n);  
    if(xi==1||xi==n-1)return true;  
    for(int i=0;i<exp-1;i++){  
        xi=xi*xi%n;  
        if(xi==1)return false;  
        if(xi==n-1)return true;  
    }  
    return false;  
  
}  
Int b,mx,mn;  
int main() {  
    ios_base::sync_with_stdio(0);  
//    putchar(suspect(3,121)?'y':'n');  
    int ff=0;  
    while(~scanf("%llu%llu%llu",&b,&mn,&mx)&&b+mn+mx){  
        Int omn=mn,omx=mx;  
        vector<Int> ans;  
        int op=0;  
        if(!(mn&1))mn++;  
        if(!(mx&1))mx--;  
        for(Int i=mn;i<=mx;i+=2){  
//            printf("%lld\\n",i);  
            bool isp=false;  
            if(suspect(2,i)&&suspect(7,i)&&suspect(61,i)){  
                isp=true;  
            }else{  
                op++;  
            }  
            if((i&1)&&suspect(b,i)==true&&isp==false){  
                ans.PB(i);  
            }  
        }  
        int size=ans.size();  
        if(ff++)Pln();  
        printf("There are %d odd non-prime numbers between %llu and %llu.\\n",op,omn,omx);  
        if(size){  
            printf("%d suspects fail in base %llu:\\n",size,b);  
            FOR(it,ans){  
                printf("%lld\\n",*it);  
            }  
        }else printf("There are no failures in base %llu.\\n",b);  
    }  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
}  

Loading...
Ownership of this post data is guaranteed by blockchain and smart contracts to the creator alone.