Adjacency List
An adjacency list is a data structure used to represent a graph, where each node stores a list of its adjacent nodes (i.e., nodes directly connected by edges). It is efficient for sparse graphs and commonly implemented using arrays of linked lists, dictionaries, or arrays of arrays. This structure allows for quick traversal of neighbors and is memory-efficient when the graph has few edges relative to nodes.
Developers should learn and use adjacency lists when working with graph algorithms, such as breadth-first search (BFS), depth-first search (DFS), or Dijkstra's algorithm, especially in scenarios like social networks, web page linking, or network routing where graphs are often sparse. It is preferred over adjacency matrices for memory savings and faster neighbor iteration in applications with dynamic edge additions or deletions.