Arrays

1. Arrays intro
2. Array elements - indexing
3. Array iterate over (each, each_with_index)
4. Array push, append, <<
5. Empty array
6. Count digits
7. Operations on arrays
8. Add arrays
9. Repeat arrays
10. Select (filter, grep)
11. Reject (negative filter, grep)
12. Transform with map
13. Sample from array
14. Shuffle array
15. join
16. Remove nil elements
17. Create Array with nil
18. Does array include a value
19. Delete element from array by value
20. Delete element from array by location
21. Insert element into array at location
22. Arrays shift - remove first element
23. Arrays uniq elements
24. First element of the array
25. Permutations