The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

**Running time:** 2ms

**Assessment:** This was when I switched from C++ to Java, and this solution is a lot better than my C++ solution. This one finishes, and finishes pretty quickly.

public class Problem003b { public static void main(String[] args) { long begin = System.currentTimeMillis(); long n=600851475143L; for (long i = 2; i <= n; i++) { if (n % i==0) { System.out.println(i); n = n / i; i = 2; } } long end = System.currentTimeMillis(); System.out.println(end-begin + "ms"); } }

Read the question first man then post the solutions. this is worst solution I ever seen in my life of any problem

Cool story bro.

This works perfectly except I think you have an error in your condition in the for loop. It should be for(long i = 2; i < n; i++), otherwise you'd end up with n=1.

This is one of the worst solutions and in a case if you’re giving such a solution in a job interview, then it might affect adversely the chances of getting selected.

A much better solution would be some thing like this:

#include

#include

void main()

{

long int inputnum=600851475143;

int primefactor=0;

while(inputnum%2==0)

{

inputnum=inputnum/2;

primefactor=2;

}

for(int i=3;i<=inputnum;i++)

{

while(inputnum%i==0)

{

inputnum=inputnum/i;

primefactor=i;

}

}

cout<<primefactor

}

//

//after the cout

cout<<primefactor;

return;

}

#include

#include

using namespace std;

int main()

{

long int inputnum=600851475143;

int primefactor=0;

while(inputnum%2==0)

{

inputnum=inputnum/2;

primefactor=2;

}

for(int i=3;i<=inputnum;i++)

{

while(inputnum%i==0)

{

inputnum=inputnum/i;

primefactor=i;

}

}

cout<<primefactor;

return 0;

}