vierekkäisyyslista

A "vierekkäisyyslista" is a Finnish term that translates to "adjacency list" in English, commonly used in computer science and graph theory. It is a method for representing a graph, which is a collection of vertices (or nodes) and edges that connect them.

In an adjacency list representation, for each vertex in the graph, there is a list of all vertices that are adjacent to it. Adjacency means that there is an edge connecting the two vertices. This representation is particularly useful for sparse graphs, where the number of edges is much smaller than the maximum possible number of edges.

Each vertex is typically associated with a data structure, often an array or a linked list, that stores the identifiers of its neighboring vertices. For example, if vertex A is connected to vertices B and C, the adjacency list for A would contain B and C.

The primary advantage of using an adjacency list is its efficiency in terms of space complexity, especially for sparse graphs. It also allows for quick iteration over the neighbors of a given vertex, which is beneficial for many graph traversal algorithms like Breadth-First Search (BFS) and Depth-First Search (DFS). The time complexity for checking if an edge exists between two vertices is generally proportional to the degree of the vertex in question.