Adjacency List
Domain: Data Structures
🎯 Motivation
For sparse graphs (few edges relative to nodes), an adjacency list stores each node’s neighbours separately, saving memory.
📋 Concrete Example
graph = {'A': ['B', 'C'], 'B': ['A', 'D'], 'C': ['A'], 'D': ['B']}. Each key lists only its direct neighbours.
🔗 Analogy
A contacts list on your phone. Each person’s name has a list of their direct friends. You do not store every possible friendship, only the ones that exist.