Connected Components in Graphs

Jul 24, 2024

Notes on Connected Components in Graphs

Introduction

  • Connected Components: Essential concept in graph theory.
  • Reminder: Graphs can take various forms (e.g., binary trees).

Definition and Examples

  • A graph can consist of several disjoint parts:
    • Example with nodes and edges given.
    • Nodes can form distinct components but still be part of a single graph.
  • Importance of recognizing all individual components:
    • Four Components Example:
      • Components can be defined even if they are not connected (like isolated nodes).
  • Clarification: A graph may seem like multiple graphs but can consist of multiple components.

Traversal Algorithms

  • Any traversal algorithm must account for connected components.
  • When traversing a graph:
    • Start from an unvisited node and explore its connected components thoroughly.
    • Visited nodes should be tracked using a Visited Array:
      • Example: An array with a size of 11 (for nodes 1 to 10).

Steps in Traversal

  1. Initialization: Mark all nodes as unvisited (set to false).
  2. Traversal for Each Node:
    • Loop through nodes 1 to 10:
      • If a node is unvisited, initiate traversal from that node.
  3. Traversal Explanation:
    • When initiated, the algorithm explores all reachable nodes and marks them as visited.
    • Example walkthrough:
      • From node 1, it travels to nodes 2, 4, and 3, marking them as visited.
      • Move to next unvisited node (e.g. node 5, then 6, 7).
      • Continue this process until all nodes are traversed.

Key Takeaway

  • Important to ensure all components are considered: If the graph has several components, starting from only one node (e.g., node 1) will not cover or reach all other components.
  • Always check each node sequentially to ensure full component traversal.

Conclusion

  • Understanding connected components is crucial for effective graph traversal.
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