LEVEL 3 OF 5

Advanced Data Structures

Organize data for more powerful operations.

Trees

A node owns smaller subtrees. Many global answers can be assembled from child answers.

Ordering applies to whole subtrees: every left descendant is smaller and every right descendant is greater under a strict-key policy.

Keep the best-priority item at the root while maintaining only parent–child order, rather than sorting every element.

Share character-by-character paths so every node represents a prefix and can retain information about words with that prefix.

Model entities as vertices and relationships as edges, including implicit edges in a grid.