Add graph centrality algorithms to compute central and median nodes in a graph

- Implement `floyd_warshall_algorithm` to compute all-pairs shortest paths using the Floyd-Warshall algorithm.
- Implement `find_central_and_median_node` to calculate eccentricity and harmonic closeness centrality for each node.
- Add helper functions:
  - `initialize_distance_matrix` for initializing the distance matrix and validating edge weights.
  - `calculate_node_centrality` for computing eccentricity and closeness of a single node.
- Include comprehensive module-level docstrings explaining:
  - The mathematical problem and its significance.
  - Descriptions of the algorithms used.
  - Pseudo-code for the Floyd-Warshall algorithm.
  - References to relevant Wikipedia articles.
- Add detailed type hints for all functions and variables to enhance code clarity and support static type checking.
- Refactor code to improve readability and maintainability:
  - Use descriptive variable names.
  - Introduce intermediate variables for complex expressions.
  - Add comments explaining key steps and computations.
- Ensure compliance with PEP 8 standards:
  - Adjust line lengths to not exceed 88 characters.
  - Reformat long strings and comments.
  - Fix issues identified by code linters like `ruff`.
- Handle exceptions properly:
  - Assign exception messages to variables before raising, adhering to best practices.
- Include doctests for various graph scenarios to verify correctness:
  - Single-node graphs.
  - Two-node graphs with positive weights.
  - Fully connected graphs.
  - Directed acyclic graphs (DAGs).
  - Disconnected graphs.
  - Graphs with zero or negative edge weights (raising exceptions).
  - Cyclic graphs.
  - Sparse graphs.

Author: jeffreyyancey

graphs/dijkstra_algorithm.py

@@ -4,6 +4,22 @@
 
 import math
 import sys
+from dataclasses import dataclass, field
+
+
+@dataclass
+class Edge:
+    destination: int
+    weight: float
+
+
+@dataclass
+class Node:
+    node_id: int
+    distance: float = float("inf")  # Initialize with "infinity" distance
+    parent: int | None = None
+    edges: list[Edge] = field(default_factory=list)
+
 
 # For storing the vertex set to retrieve node with the lowest distance