# Binary Search Tree in Elixir

#### Insert and search for numbers in a binary tree.

1 | ```
exercism fetch elixir 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:

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

If we then added 3, it would look like this

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

## Running tests

Execute the tests with:

1 |
```
$ elixir binary_search_tree_test.exs
``` |

### Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by
commenting out the relevant `@tag :pending`

with a `#`

symbol.

For example:

Or, you can enable all the tests by commenting out the
`ExUnit.configure`

line in the test suite.

1 |
```
# ExUnit.configure exclude: :pending, trace: true
``` |

For more detailed information about the Elixir track, please see the help page.

## Source

Josh Cheek https://twitter.com/josh_cheek

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.