# Code Challenge #11: June 21, 2017

Every week, we feature the type of brain-teasing question that might be asked in a full-stack developer’s job interview at places such as Google and Facebook.

This week’s challenge is a very common interview question and was reported to have been asked in interviews at many top companies including **Google**:

### Basic Difficulty

Write a function,

`fibonacciFinder50`

, that will find the 50th number in the Fibonacci Sequence.

**Function Name**:`fibonacciFinder50`

**Input**: There are no parameters to this function**Output**: an integer, the 50th number in the Fibonacci Sequence**Example**:`fibonacciFinder50() => 7778742049`

- In the Fibonacci Sequence, the first two numbers are
`0`

and`1`

and every number thereafter is the sum of the previous two numbers in the sequence - For this challenge, consider
`0`

to be the`1st`

Fibonacci Number, not the`0th`

(i.e. do not zero-index)

##### Find out more about basic challenges.

### Intermediate difficulty

Write a function,

`fibonacciFinderN`

, that will find the`n`

th number in the Fibonacci Sequence.

**Function Name**:`fibonacciFinderN`

**Input**: any integer,`n`

, where`n`

is a natural number (in this case not including 0)**Output**: an integer, the`n`

th number in the Fibonacci Series**Example**:`fibonacciFinderN(300) => 137347080577163115432025771710279131845700275212767467264610201`

- Please use this example – the 300th Fibonacci Number – with your submission

##### Find out more about intermediate challenges.

### Hard Difficulty

Write

`fibonacciFinderN`

as efficiently as possible.

- Can you solve this challenge in
`O(n)`

time complexity? - Many of you will still find that this challenge is too easy (and this is not unusual), so see how you can stretch yourself further. Can you solve this problem in an unorthodox or elegant way? How about in a different language? Take this opportunity to show off your scripting skills and creative outside-the-box thinking!

##### Find out more about hard challenges and Big O

`Reply`

to this thread with a link to your code on repl.it *and* paste your properly formatted code to participate! Don’t just submit your code, remember to `explain`

your solution, too! If you want to be considered as the winner, your function `must`

have the `correct name`

and provide `output in the format specified`

above, you also need to abide by our other simple rules.

As always solutions using imports to do all the heavy lifting such as `itertools`

will not be considered for the winner.

**The fine print:**

Click the links to find out more about:

- the rules & how to participate in challenges
- how challenges are used as job interview questions
- why Codecademy runs challenges (and why they are formatted this way)
- more details about the challenges and why we think they are useful.
- find previous challenges (and see the past winners) in our Challenge Index