10006 - Carmichael Numbers

[sohag144]

Is there anyone to help me.
code deleted.
although it outputs correctly judge says wrong answer.please help.

[Artikali]

try these charmicheal numbers
62745,63973
your code answered normal numbers

[sohag144]

yeh.i found my bug , i have to use long long in bigmod() function.

[johnplayers]

That was very helpful!!
Thnx

[willima]

I solved this problem by precalculating the Carmichael Numbers and, from the topics above, I think this is the only to solve the problem without TLE. Am I right?

[vijay03]

Here is my code I do not understand why this out Wrong Ans:..Plz Help me.....
#include<stdio.h>
int main()
{
int i;
long input,array[15]={561,1105,1729,2465,2821,6601,8911,10585,15841,29341,41041,46657,52633,62745,63973};
while(scanf("%ld",&input)==1)
{
if(input==0) break;
int k=0;
for(i=0;i<=14;i++)
{
if(input==array)
{
printf("The number %ld is a Charmichael number.\n",input);
k++;
break;
}
}
if(k==0) printf("%ld is normal.\n",input);
}
return 0;
}

The OJ says to print "The number 561 is a Carmichael number.".. while yours prints out "The number 561 is a Charmichael number"..

[flehns]

My computer runs my code so quickly, and gets all of the answers right, but it still gets TLE. I have taken all the advice I could from the boards and even took into account the possibility of entering a value that is not an integer. I am getting pretty frustrated seeing TLE so much.

Code: Select all

#include <iostream>
#include <cmath>
#include <vector>
using namespace std;

//adapted from prime_factorization()
bool isPrime(unsigned long x)
{
	unsigned long i;			/* counter */
	unsigned long c;			/* remaining product to factor */

	c = x;

	while ((c % 2) == 0) {
		//printf("%ld\n",2);
		c = c / 2;
	}

	i = 3;

	while (i <= (sqrt((double)c)+1)) {
		if ((c % i) == 0) {
			//printf("%ld\n",i);
			c = c / i;
		}
		else
			i = i + 2;
	}

	if (c > 1) return (c == x);
	return 0;
}

//calculates a^n(mod n)
unsigned long fermat(unsigned long a,unsigned long totheN,unsigned long modN) {
	if (totheN==0)
		return 1;
	else if (totheN==1)
		return a%modN; 
	else if (totheN%2==0)
		return (fermat(a,totheN/2,modN)*fermat(a,totheN/2,modN))%modN;
	else
		return ((a%modN)*(fermat(a,totheN-1,modN)%modN))%modN;
}

bool carmnumber(unsigned long n)
{
		for(unsigned int i = 2; i < n; i++)
		{
			if(i == fermat(i,n,n))
			{
				if(isPrime(n)) { return 0; break; }
				return 1;
				break;
			}
			else
			{	return 0;
				break;
			}
		}
}

int main()
{
	double n;
	cin >> n;
	

	while(n != 0)
	{
		if((n-(int)n) > 0) { cout << n << " is normal.\n"; }
		else {
		if(carmnumber((unsigned long)n)) { cout << "The number " << n << " is a Carmichael number.\n"; }
		else { cout << n << " is normal.\n"; }
		}
		cin >> n;
	}
}

When I try to pre-generate, my computer freezes. Please help!

[flehns]

Can someone give me a hint as to how to precalculate. I tried to precalculate by running through all the numbers from 2 to 65000 and putting it into an array if it was a carmichael number, but this wound up taking sooo much time.

[willima]

Can someone give me a hint as to how to precalculate. I tried to precalculate by running through all the numbers from 2 to 65000 and putting it into an array if it was a carmichael number, but this wound up taking sooo much time.

Well, precalculating really can take several seconds or even minutes, depending on what platform you use. So, what you can do is run a program that calculate this numbers and another program that returns this number instantly, using a switch case structure.

I coudn't imagine another way to solve the problem.

Good luck!

[newton]

going to the link

http://www.comp.nus.edu.sg/~stevenha/pr ... l%20Number

i came to know that the number has exactly 3 or greater prime factor;
but i am confused that why 30 is not a carmaichel number?

30 = (3*5*2);


i know there is a wrong with me. but what is that?
may anyone explaine it?





newton............ simply the best

[rio]

The link you posted doesn't have enough explanation.

I think this link would be enough to answer your question.
http://mathworld.wolfram.com/CarmichaelNumber.html

[newton]

Code: Select all

          resolved after AC

thanks, it was a chilly mistake








NEWTON...................... SIMPLY THE BEST!

[tgoulart]

Well, instead of 'Charmichael' you should print 'Carmichael'. =]

[andmej]

Oh, my god. I just found the silliest bug of my life. I was printing

1729 is a Carmichael number.

instead of

The number 1729 is a Carmichael number.

Almost lost my head trying to find where the WA was...

[adhoc17]

i m getting wrong answer in this problem.
it seems to work correctly for all inputs including the 15 carmichael numbers in the range specified.
could anyone plz help me?
my code follows:




#include<iostream>
#include<cmath>
using namespace std;
int isprime(long n)
{ int i;
if(n==1||n==2)
return 0;
for(i=3;i<=(int)sqrt(n)+1;i+=2)
{
if(n%i==0)
return 0;
}
return 1;
}


int expm(long n)
{ unsigned long x,y,m,j;
for( j=2;j<n-1&&!isprime(j);j++)
{
x=1;
y=j;
m=n;
while( m>0)
{
if(m%2==1)
x=((x%n)*(y%n))%n;

y=((y%n)*(y%n))%n;
m/=2;

}
if(x%n!=j)
return 0;
}
return 1;

}



main()
{
unsigned long n;
while(1)
{
cin>>n;
if(n==0)
break;
if(isprime(n)==0&&expm(n)==1)
cout<<"The number "<<n<<" is a Carmichael number."<<endl;
else
cout<<n<<" is normal."<<endl;
}

return 0;
}

help me plz.