calculating n factorial

[becky808]

Hi,

I'm trying to write a program to calculate n factorial but it won't compile. Can anyone tell me what I'm doing wrong?

#include <iostream>
#include <cmath>

using namespace std;
int main(){

int n;
float factorial;
float lnFactorial;

cout << "Please enter a positive integer:" << endl;
cin >> n;

{
if (n%2 == 0){

}
else if ((n+1)%2==0){

}
else {
cout << "Please enter a positive integer:" << endl;
}
}
if (n<0){
cout << "Please enter a positive integer:" << endl;
cin >> n;
}
else if(n==0){
cout <<"n! == 1" << endl;
}
else if(n<=50) {
{for(int i=n; i>=1; i--){
factorial *= i;
}

cout << "n! == " << factorial << endl;
}
else{
{lnFactorial = (n*log(n)) - n;
factorial = exp(lnFactorial);
}
cout <<"n! == " << factorial << endl;
}

return 0;
}

[archonmagnus]

For one thing, it looks like you have an excess in the number of braces you have. Specifically, in the segment:

    else if(n<=50)
    {
        {for(int i=n; i>=1; i--)
        {
            factorial *= i;
        }
 
        cout << "n! == " << factorial << endl;
    }
    else
    {
        {lnFactorial = (n*log(n)) - n;
        factorial = exp(lnFactorial);
        }
        cout <<"n! == " << factorial << endl;
    }
 

You have extra braces preceeding "for(int i=n; i>=1; i--)" and "InFactorial = (n*log(n)) - n;". Please don't think I'm criticizing your code, but if I may suggest using a better visualization/spacing technique, it would help you to be able to see these fixes a bit easier.

[whodgson]

I suggest you write a simple factorial fuction and then a basic test driver. You can write a fancy main later. Also it would help if you enclosed your

code

say:

double fact (int n)
{
    if (n<0) return 0;
      double f=1;
       while(n>1)
          f*=n--;
          return f;
}

you can substitute your function for the above later after it compiles and runs properly The test driver only needs a for loop from within which you call fact()