prime number finder.

This is a discussion on prime number finder. within the C++ Programming forums, part of the General Programming Boards category; well the other day i noticed that the diferance between 2 perfect squares is a prime number, so i made ...

  1. #1
    Registered User Aalmaron's Avatar
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    prime number finder.

    well the other day i noticed that the diferance between 2 perfect squares is a prime number, so i made a program that does the math for you.


    Code:
    #include<iostream>
    using namespace std;
    int counter = 1;
    int main()
    {
    int num1;
    
      do
      {
    
        cout << "enter a number: ";
        cin >> num1;
        int num2 =  num1 + 1;
        int square1 = num1 * num1;
        int square2 = num2 * num2;
        int prime = square2 - square1;
        cout << "your prime number is: " << prime << endl;
          
      }
      while (counter = 1);
    
      cin.get();
      return 0;
    }
    yeah i couldnt get a "yes/no would you like to do it again" thing to work, so i just made it loop like that.

    also, dont try to enter a letter, it spazzes out.

  2. #2
    Senior Member joshdick's Avatar
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    5^2 = 25
    4^2 = 16

    25 - 16 = 9, which is not a prime.

    I regret to inform you that your theorem doesn't hold, but I genuinely applaud your interest in number theory. I suggest getting a book on the subject or taking a course in it. It's good stuff.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  3. #3
    Registered User Aalmaron's Avatar
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    damnit, i just came to inform you of that, heh.

    i've been testing it all morning and just decided to work with the small numbers, damn small numbers make me feal stupid lol

    i tested up to getting the answer 65. here are my results. number i put in)number i got(numbers its devisible by
    4)9(3
    7)15(3,5
    10)21(7
    12)25(5
    17)35(5,7
    22)45(5,9-15,3
    24)49(7
    27)55(5,11
    32)65(5,13

    it seems that its almost true, except for being devisible by the prime numbers themselves, and - in the of 22, a number previouly gotten.

    i still have work. thanks for wasting your time to read that
    Last edited by Aalmaron; 03-05-2004 at 05:09 PM.

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