diff --git a/recitation-sessions/recitation-session-1.md b/recitation-sessions/recitation-session-1.md new file mode 100644 index 0000000000000000000000000000000000000000..2c895307c187a06a2b120dd82128bf52b5ca7d79 --- /dev/null +++ b/recitation-sessions/recitation-session-1.md @@ -0,0 +1,59 @@ +# Recitation Session 1 + +We will work on tail recursion in this session. + +## Exercise 1: Factorial + +Recall the factorial function that you saw in class + +```scala +def factorial(n: Int): Int = if (n <= 0) 1 else n * factorial(n - 1) +``` + +Define a tail recursive version of it + +```scala +def factorial(n: Int): Int = fact(n, 1) +@tailrec +def fact(n: Int, acc: Int): Int = ??? +``` + +What would be the advantage of making `fact` an inner function to `factorial`? + +## Exercise 2: Sum of elements on a list + +Define a function that takes a list of integers and sums them. You can use the functions `head`, `tail`, and `isEmpty` on lists, as you have seen for your homework. + +```scala +def sumList(ls: List[Int]): Int = ??? +``` + +Convert your definition into a tail-recursive one. + +## Exercise 3: Fast exponentiation + +Fast exponentiation is a technique to optimize the exponentiation of numbers: + +``` +b²⿠= (b²)â¿ = (bâ¿)² +b²â¿âºÂ¹ = b * b²⿠+``` + +Define a function that implements this fast exponentiation. Can you define a tail recursive version as well? + +```scala +def fastExp(base: Int, exp: Int): Int = ??? +``` + +## Exercise 4: Tail recursive Fibonacci + +Define a function that computes the nth Fibonacci number. Can you define a tail recursive version as well? The Fibonacci recurrence is given as follows: + +``` +fib(n) = 1 | n = 0, 1 +fib(n) = fib(n - 1) + fib(n - 2) | otherwise +``` + +```scala +def fibonacci(n: Int): Int = ??? +```