Java solution to Project Euler Problem 3

Problem 3:

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.

6 thoughts on “Java solution to Project Euler Problem 3

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

  2. 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.

  3. 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
    }

    //

  4. #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;

    }

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