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Help c++ program: conditions

  1. Oct 16, 2006 #1
    I need to write a program that prompts me to enter a positive integer N, after doing so it calculates the factorial of that integer and prints it. I am able to do this with the following code.

    #include <iostream>
    using namespace std;
    int main()
    double I, N, Factorial = 1; // Do not forget to initialize Factorial
    cout << "Enter a positive integer:" << endl;
    cin >> N;
    I = 1; // This initialization step has to be done. And it must be done before the while loop.
    while (I <= N) // Notice there is no semicolon here.
    Factorial = Factorial * I; // The body of the loop begins here.
    I = I + 1; // You must increment I. The body of the loop ends here.
    cout << Factorial << endl;
    return 0;

    I now however need to create the condition that IF the integer is greater than 50, I need to apply Stirling's approximation which is = N (NaturalLog(N)) - N. I also need the program to initially check whether or not the integer is positive, and if not to prompt to re-enter.

    Can anyone help??
  2. jcsd
  3. Oct 16, 2006 #2


    User Avatar
    Science Advisor

    The first is just a simple if statement. You'll need to include a math library to get the log. For the second, you should loop until the integer is positive. That is, you input the integer the first time, and then enter a loop so that while the integer is not positive, you tell them so and ask them for it again.
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