Jamisco - 6 months ago 37

C# Question

`using System;`

namespace CalculatorApplication

{

class NumberManipulator

{

public int factorial(int num)

{

/* local variable declaration */

int result;

if (num == 1)

{

return 1;

}

else

{

result = factorial(num - 1) * num;

return result;

}

}

static void Main(string[] args)

{

NumberManipulator n = new NumberManipulator();

//calling the factorial method

Console.WriteLine("Factorial of 6 is : {0}", n.factorial(6));

Console.WriteLine("Factorial of 7 is : {0}", n.factorial(7));

Console.WriteLine("Factorial of 8 is : {0}", n.factorial(8));

Console.ReadLine();

}

}

}

so i know it has to do with the function being a recursion but how is the code able to know when to keep multiplying the integers less than 6 in order to find the factorial. Also how does the code know when to stop multiplying when it reaches 6. If this was in a loop i could fully understand how this would be possible but with no loop i just do not understand.

I'm still in the tutorial of learning c#, if you can please try to keep it as simple as possible.

Any help would be greatly appreciated.

Answer

Let's step through `factorial(6)`

.

What's `factorial(6)`

? `factorial(5) * 6`

.

What's `factorial(5)`

? `factorial(4) * 5`

.

What's `factorial(4)`

? `factorial(3) * 4`

.

What's `factorial(3)`

? `factorial(2) * 3`

.

What's `factorial(2)`

? `factorial(1) * 2`

.

What's `factorial(1)`

? `1`

.

You then just go backward from there and you'll arrive at your answer:

`factorial(6)`

= `1 * 2 * 3 * 4 * 5 * 6`

.