Challenge: Tail Recursion

Test yourself and implement what you have learned so far in this challenge.

We'll cover the following

Problem Statement

In a previous lesson on recursion, we implemented the recursive factorial function. You need to design a tail-recursive version of the factorial function given below.

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def factorial(x: Int) : Int = {
  if(x == 1)
    1
  else
    x * factorial(x-1)
}
// Driver Code
print(factorial(3))

The tail recursive version of factorial requires a nested function loop. loop has two parameters: accumulator and x and is the tail recursive part of factorial. All you have to do is figure out what the function body of loop should contain.

Input

The input of the function is a number x of type Int whose factorial value you want to compute.

Output

The output will be the factorial of x.

Sample Input

5

Sample Output

120

Test Yourself

Write your code in the given area. Try the exercise by yourself first, but if you get stuck, the solution has been provided. Good luck!

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def factorial(x: Int): Int = {
  def loop(accumulator: Int, x: Int): Int = {
    // Write your code here
    return -1 // Remove this line after writing your code
  }  
  loop(1,x)
}

Let’s go over the solution review in the next lesson.