Question

C++ only

Implement a program that prompts a user to enter a number N where N is a positive number. The program must validate a user input and ask a user to re-enter until an input is valid. Implement a function that pass N as an argument and return a result of calculates N! (N-factorial):

The function must use loop for the implementation.

Hint: Factorial: N! = N * (N-1) * (N-2) * …. * 1 ( This is only a hint of how to calculate the factorial not the output)

The output of the program must be exactly match the example.

Examples: Enter an integer: 7
7! = 5040

Examples: Enter an integer: 6
6! = 720

Examples: Enter an integer: -2

An input must be positive. Please try again!

Enter an integer: 4

4! = 24

Answer 1

#include <iostream>

using namespace std;

int Factorial(int n){
   if(n<0){
      return 0;
   }
   else if(n <= 1){
      return 1;
   }
   return n*Factorial(n-1);
}

int main()
{
   int n = -1;
   while(n<0){
      cout << "Enter a number: ";
      cin >> n;
      if(n<0){
         cout<<"An input must be positive. Please try again!"<<endl;
      }
   }
   cout << n <<"! = " << Factorial(n) << endl;
   return 0;
}

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