Question

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 1

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;
19. if(n <= 7){
20. cout<<"Factorial is "<< factorial(n);
21. }else{
22. cout<<"Wrong input number.";
23. }
25. return 0;
26. }

Step-by-step 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.