What is a binary tree?

A binary tree is a data structure in which each node can have at most two children:

• a left child
• a right child

#Structure

Here:

• A is the root,
• B and C are children of A,
• B has two children (D and E),
• C is a leaf (no children).

#Features

• Each node has up to 2 edges (unlike a general tree, where it can have more).
• Simplifies the implementation of search, sorting, and traversal.

#Main types

1. Complete - every level is filled except possibly the last, and the elements in it are arranged left to right.
2. Perfect - every level is fully filled.
3. Balanced - the height of the left and right subtrees differs by no more than 1.
4. Binary search tree (BST) - the left subtree contains elements smaller than the parent, the right subtree contains larger ones.

#Summary

A binary tree is a hierarchical structure in which each node is connected to at most two children, which makes it the basis for many search, sorting, and data-storage algorithms.