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Write a function factorial() that takes a positive integer as a parameter and returns the factorial of that integer. The main function takes an integer n<=7, as input, and utilizes the factorial function to calculate the following series.

Answer :

teobguan2019

Answer:

The solution code is written in C++:

  1. #include <iostream>
  3. using namespace std;
  5. int factorial(int n){
  6.    if(n == 1){
  7.        return n;
  8.    }else{
  9.        return n * factorial(n-1);
  10.    }
  11. }
  13. int main()
  14. {
  15.    int n;
  16.    cout<<"Please enter a number <= 7 :";
  17.    cin>>n;
  18.    
  19.    if(n <= 7){
  20.        cout<<"Factorial is "<< factorial(n);
  21.    }else{
  22.        cout<<"Wrong input number.";
  23.    }
  25.    return 0;
  26. }

Explanation:

Firstly, create a function factorial with one input parameter (Line 1).

Next, create an if-else statement to check if input n is 1, just return the end (Line 6-7).

Otherwise, the function should return n multiplied by output of the recursive calling of the function itself (Line 8-9).

In the main program, create variable and prompt user to input number (Line 15 -17).

Next, do the input validation checking to ensure the input n must be equal or less than 7 then only call factorial function to calculate the factorial of n and display the answer (Line 19 - 20). Otherwise, the program shall just display error message.

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