Advanced Graph Algorithms in C#

using System;
using System.Collections.Generic;

class Node : IComparable<Node> {
    public string Id { get; }
    public int Distance { get; }

    public Node(string id, int distance) {
        Id = id;
        Distance = distance;
    }

    public int CompareTo(Node other) {
        return Distance.CompareTo(other.Distance);
    }
}

class Dijkstra {

    public static Dictionary<string, int> DijkstraAlgorithm(Dictionary<string, Dictionary<string, int>> graph, string start) {
        var minHeap = new PriorityQueue<Node, int>();
        minHeap.Enqueue(new Node(start, 0), 0);
        var dist = new Dictionary<string, int> {
            { start, 0 }
        };

        while (minHeap.Count > 0) {
            var currentNode = minHeap.Dequeue();
            var u = currentNode.Id;
            var currentDist = currentNode.Distance;

            if (currentDist > dist.GetValueOrDefault(u, int.MaxValue)) {
                continue;
            }

            foreach (var neighbor in graph.GetValueOrDefault(u, new Dictionary<string, int>())) {
                var v = neighbor.Key;
                var weight = neighbor.Value;
                var distance = currentDist + weight;

                if (distance < dist.GetValueOrDefault(v, int.MaxValue)) {
                    dist[v] = distance;
                    minHeap.Enqueue(new Node(v, distance), distance);
                }
            }
        }

        return dist;
    }

    public static void Main(string[] args) {
        var graph = new Dictionary<string, Dictionary<string, int>> {
            { "A", new Dictionary<string, int> { { "B", 1 }, { "C", 4 } } },
            { "B", new Dictionary<string, int> { { "A", 1 }, { "C", 2 }, { "D", 5 } } },
            { "C", new Dictionary<string, int> { { "A", 4 }, { "B", 2 }, { "D", 1 } } },
            { "D", new Dictionary<string, int> { { "B", 5 }, { "C", 1 } } }
        };

        var result = DijkstraAlgorithm(graph, "A");
        foreach (var entry in result) {
            Console.WriteLine($"{entry.Key} = {entry.Value}");
        }
        // Output: A = 0, B = 1, C = 3, D = 4
    }
}