Run the tests in the spec folder, and write your code in bubble_sort.rb.

Keep in mind all the different ways you can explore your code:

From the Command Line:

ruby bubble_sort.rb # just make sure you're printing some output!

In the REPL:

irb
# or
pry

pry > require "bubble_sort.rb"
pry > bubble_sort([3,2,1])

Using Rspec Tests:

rspec
# or
rspec spec/bubble_sort_spec.rb
# or, run an individual test
rspec -e "handles zero"

Pre-work: First, some Hungarian ("Csángó") folk dance

Bubble sort is one of the first sorting algorithms you should try and master. It essentially forces larger elements to 'sink' to the bottom/back while inadvertently 'floating' smaller elements to the top/front of a list. This is done with numerous comparisons between one element in an array with its neighbor.

Look at the first two elements in the list.

0: [5, 4,2,3,1,6]

Is 5 > 4 ? Yes! Swap!

If an element on the left (5) is greater than the element on the right (4), the two elements 'swap' locations

1: [4,5,2,3,1,6]

2: [4,2,5,3,1,6]

3: [4,2,3,5,1,6]

4: [4,2,3,1,5,6]

Important: We now know that the last element in the list is the largest element in the list. There's no need to do a comparison with that number ever again.

0: [4,2,3,1,5,6]

1: [2,4,3,1,5,6]

2: [2,3,4,1,5,6]

3: [2,3,1,4,5,6]

Stop!

Remember: we know that last element is the largest number in the list. There is no need to compare against that number ever again. We also now know that the second to last number is the second largest number; no need to move that one ever again as well. (Detect a trend?)

0: [2,3,1,4,5,6]

If an element on the left has met a larger or equal element, we look at its bigger neighbor and now compare the larger neighbor to it's neighbor on the right. The process is continued until our established end.

1: [2,3,1,4,5,6]

2: [2,1,3,4,5,6]

Stop!

We don't stop sorting until we hit the end. Even if we find

0: [2,1,3,4,5,6]

1: [1,2,3,4,5,6]

Stop!

0: [1,2,3,4,5,6]

Stop!

When there is only one element (the first element) left in our unsorted list, it is already sorted for us as a freebie!