Functions 2

1. Numbers passed by reference
2. Array passed by value or by reference
3. TODO: pass by value, pass by reference
4. Variable declaration outside of functions
5. Exercise: Fibonacci series
6. Exercise: Permutations
7. Exercise: 100 doors
8. Solution: Fibonacci series
9. Solution: Fibonacci recursive
10. Solution: single counter
11. Solution: Permutations
12. Solution: 100 doors
13. TODO return array