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What is a tree as a data structure?

Data StructuresJunior~1 min read
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A tree is a hierarchical data structure in which every element (called a node) can have child nodes, but only one parent (except the root).

Key concepts

  • Root - the top node, which has no parent.
  • Children - nodes that branch out from a parent.
  • Leaves - nodes with no children.
  • Edge - the connection between a parent and a child.
  • Tree height - the length of the longest path from the root to a leaf.

The core idea

A tree stores data as a hierarchy, not in a linear order (like a list or a queue).

Example

javascript
A ← root / \ B C ← children of A / \ D E ← leaves

Common types of trees

  • Binary tree - each node has at most two children.
  • Search tree (BST) - left child < parent < right child.
  • Prefix tree (Trie) - used to store strings and support autocomplete.
  • AVL, red-black tree - balanced variants that speed up search.

Summary

A tree is a structure where data is organized by levels, which makes search, sorting, hierarchical storage, and traversal efficient.

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