1 exercism fetch ruby binary-search-tree

# Binary Search Tree

Insert and search for numbers in a binary tree.

When we need to represent sorted data, an array does not make a good data structure.

Say we have the array [1, 3, 4, 5], and we add 2 to it so it becomes [1, 3, 4, 5, 2] now we must sort the entire array again! We can improve on this by realizing that we only need to make space for the new item [1, nil, 3, 4, 5], and then adding the item in the space we added. But this still requires us to shift many elements down by one.

Binary Search Trees, however, can operate on sorted data much more efficiently.

A binary search tree consists of a series of connected nodes. Each node contains a piece of data (e.g. the number 3), a variable named left, and a variable named right. The left and right variables point at nil, or other nodes. Since these other nodes in turn have other nodes beneath them, we say that the left and right variables are pointing at subtrees. All data in the left subtree is less than or equal to the current node's data, and all data in the right subtree is greater than the current node's data.

For example, if we had a node containing the data 4, and we added the data 2, our tree would look like this:

 1 2 3 4 / 2

If we then added 6, it would look like this:

 1 2 3 4 / \ 2 6

If we then added 3, it would look like this

 1 2 3 4 5 4 / \ 2 6 \ 3

And if we then added 1, 5, and 7, it would look like this

 1 2 3 4 5 6 4 / \ / \ 2 6 / \ / \ 1 3 5 7

For installation and learning resources, refer to the exercism help page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

 1 gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

In order to run the test, you can run the test file from the exercise directory. For example, if the test suite is called hello_world_test.rb, you can run the following command:

 1 ruby hello_world_test.rb

To include color from the command line:

 1 ruby -r minitest/pride hello_world_test.rb