This post is one in a series about stuff formally trained programmers know – the rest of the series can be found here.

# Binary Tree

In the previous post we looked at the tree pattern, which is a theoretical way of structuring data with many advantages. A tree is just a theory though, so what does an actual implementation of it look like? A common data structure implementation is a binary tree.

The name binary tree gives us a hint to how it is structured, each node can have at most 2 child nodes.

## Classifications

As a binary tree has some flexibility in it, a number classifications have come up to have a consistent way to discuss a binary tree. Common classifications are:
- **Full** binary tree: Each node in a binary tree can have zero, one or two child nodes. In a **full** binary tree each node can only have zero or two child nodes.
- **Perfect** binary tree: This is a full binary tree with the additional condition that all leaf nodes (i.e. nodes with no children) are at the same level/depth.
- **Complete** binary tree: The complete binary tree is where each leaf node is as far left as possible.
- **Balanced** binary tree: A balanced binary tree is a tree where the height of the tree is as small a number as possible.

# Implementations

While a binary tree is more than just a pattern, there are no out of the box implementations in C#, Java or JavaScript for it. The reason is that it is a very simple data structure and so if you need just the data structure you could implement it yourself but more importantly, you likely want more than the simple structure - you want a structure that optimises for traversal or data management.