existingNode

existingNode is a descriptive term used in data structures and algorithms to refer to a node that already exists within a structure such as a graph, tree, or network. It is typically contrasted with newNode or candidateNode, which denotes a node that is being created, added, or considered for addition.

In graph-related contexts, existingNode often appears in operations that modify the structure, such as adding edges, connecting components, or traversing paths. For example, an algorithm might require that both endpoints of a new edge are existing nodes in the graph, or it may update properties of an existingNode during a traversal. In trees and networks, existingNode helps distinguish between elements that are present versus those that are to be introduced.

Identification of an existing node can be based on a unique identifier, a permanent object reference, or a specific position within a structure. Performance characteristics depend on the underlying data structure used to track nodes: existence checks are typically O(1) with hash-based structures, O(log n) with balanced trees, or O(n) with simple lists. Correct use of existingNode also involves handling null references, ensuring consistency when multiple operations occur concurrently, and avoiding duplicates when adding new nodes.

The term is informal and context-dependent; different implementations may formalize the concept as a vertex, node ID, or reference. It is commonly encountered in graph algorithms, network models, and data-structure code where distinguishing between present and absent elements is important. See also: node, vertex, graph, edge.