Difficulty with Dijkstra's Algorithm Implementation in C# - Inaccurate Shortest Path Results in Graph with Negative Edge Weights
I'm following best practices but I'm trying to implement I'm a bit lost with I'm sure I'm missing something obvious here, but I'm working on a project and hit a roadblock... I'm currently implementing Dijkstra's algorithm in C# using the `System.Collections.Generic` library for managing my graph structure. However, I am encountering an issue where my results seem inaccurate when my graph contains negative edge weights. Specifically, my implementation returns a path that is longer than expected in certain cases. Here’s a simplified version of my code: ```csharp public class Graph { private Dictionary<int, List<(int destination, int weight)>> adjacencyList; public Graph() { adjacencyList = new Dictionary<int, List<(int destination, int weight)>>(); } public void AddEdge(int source, int destination, int weight) { if (!adjacencyList.ContainsKey(source)) adjacencyList[source] = new List<(int, int)>(); adjacencyList[source].Add((destination, weight)); } public Dictionary<int, int> Dijkstra(int start) { var distances = new Dictionary<int, int>(); var priorityQueue = new SortedSet<(int distance, int vertex)>(Comparer<(int, int)>.Create((x, y) => x.distance == y.distance ? x.vertex.CompareTo(y.vertex) : x.distance.CompareTo(y.distance))); foreach (var vertex in adjacencyList.Keys) { distances[vertex] = int.MaxValue; } distances[start] = 0; priorityQueue.Add((0, start)); while (priorityQueue.Count > 0) { var (currentDistance, currentVertex) = priorityQueue.Min; priorityQueue.Remove(priorityQueue.Min); foreach (var (neighbor, weight) in adjacencyList[currentVertex]) { int newDistance = currentDistance + weight; if (newDistance < distances[neighbor]) { distances[neighbor] = newDistance; priorityQueue.Add((newDistance, neighbor)); } } } return distances; } } ``` I’ve tried to debug the algorithm by manually tracing the paths, but the results don’t align with what I expected. For instance, when I add edges with negative weights like `graph.AddEdge(1, 2, -3);`, it seems to affect the shortest path calculations, and I end up with paths that are not optimal. The expected behavior should allow for a reliable shortest path even with negative weights, but it appears my implementation doesn’t handle this correctly. I understand that Dijkstra's algorithm is not meant for graphs with negative weights, so should I switch to Bellman-Ford instead? Or is there a way to adapt my existing code to handle negative weights appropriately? Any guidance or suggestions would be greatly appreciated! This is part of a larger CLI tool I'm building. What am I doing wrong? For context: I'm using Csharp on Ubuntu. For reference, this is a production web app. Thanks in advance! The stack includes Csharp and several other technologies. Any suggestions would be helpful. Thanks for taking the time to read this!