fibonacci1 – The Fibonacci Sequence (easy version)

Write a program that computes a number in the fibonacci sequence. This sequence is defined recursively as follows:

F₀ = 0
F₁ = 1
Fₙ = Fₙ₋₁ + Fₙ₋₂

That is, the zeroth Fibonacci number is zero and the first Fibonacci number is one. Other Fibonacci numbers are given by the sum of its two predecessors.

The Fibonacci tiling

The first 10 numbers in the Fibonacci sequence are: 0, 1, 1, 2, 3, 5, 8, 13, 21 and 34.

Input and output

Input will consist of a single integer n indicating the position in the Fibonacci sequence.

0 ≤ n ≤ 21

Output should contain a single line with a number Fₙ indicating the Fibonacci number in position n.

Example input 1

Example output 1

Example input 2

Example output 2

The `fibonacci` function

Your program should contain a fibonacci function that takes an integer and returns an integer. Please refer to the information for your chosen language:

C prototype: int fibonacci(int n)
Haskell type: fibonacci :: Int -> Int
Python definition: def fibonacci(n):
C++ prototype: int fibonacci(int n)
C# definition: public static int Fibonacci(int n) inside a public class Program
Java definition: public static int fibonacci(int n) inside a public class Fibonacci
JavaScript definition: function fibonacci(n)
Lua definition: function fibonacci (n)
Ruby definition: def factorial(n)

For the purposes of this exercise you should not worry about performance. Instead your should focus on correctness. Implement your fibonacci function in the most straightforward way possible.

Specifically for this exercise when using Python, JavaScript, Lua or Ruby, avoid using sys.exit(), process.exit(), os.exit() or exit, as your program is appended with some extra assertions in one of the test sets.

Scoring

2/12: works for the above examples albeit in an incorrect format
4/12: works for the above examples in the correct format
8/12: works for other examples
12/12: implements the fibonacci function

try first: power1

try next: hello2

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