Difficulty Implementing Dijkstra's Algorithm in C# - Incorrect Shortest Path for Weighted Graphs
I'm stuck on something that should probably be simple. I'm attempting to set up I'm stuck trying to This might be a silly question, but I'm currently trying to implement Dijkstra's algorithm in C# to find the shortest path in a weighted graph, but I'm running into issues where the calculated paths do not seem to reflect the actual shortest distances. I am using a priority queue to manage the nodes, but I'm not sure if my implementation of the relax operation is correct. Here's a simplified version of my code: ```csharp using System; using System.Collections.Generic; public class Graph { private Dictionary<int, List<(int neighbor, int weight)>> adjList = new Dictionary<int, List<(int, int)>>(); public void AddEdge(int src, int dest, int weight) { if (!adjList.ContainsKey(src)) adjList[src] = new List<(int, int)>(); if (!adjList.ContainsKey(dest)) adjList[dest] = new List<(int, int)>(); adjList[src].Add((dest, weight)); } public Dictionary<int, int> Dijkstra(int start) { var minHeap = new SortedSet<(int distance, int node)>(Comparer<(int, int)>.Create((x, y) => x.distance == y.distance ? x.node.CompareTo(y.node) : x.distance.CompareTo(y.distance))); var distances = new Dictionary<int, int>(); foreach (var node in adjList.Keys) distances[node] = int.MaxValue; distances[start] = 0; minHeap.Add((0, start)); while (minHeap.Count > 0) { var (currentDist, currentNode) = minHeap.Min; minHeap.Remove(minHeap.Min); foreach (var (neighbor, weight) in adjList[currentNode]) { var newDist = currentDist + weight; if (newDist < distances[neighbor]) { distances[neighbor] = newDist; minHeap.Add((newDist, neighbor)); } } } return distances; } } ``` When I run the algorithm on the graph represented by the following edges: - (0, 1, 4) - (0, 2, 1) - (2, 1, 2) - (1, 3, 1) The expected shortest path from node 0 to node 3 should be through node 2, yielding a total distance of 4, but my implementation is returning a distance of 5 instead. I'm not sure whether the scenario lies within my priority queue logic or during the relaxation step. I would appreciate any insights or suggestions on what might be going wrong. Are there best practices I should follow when implementing Dijkstra's algorithm that may guide to resolve this scenario? I've also tried debugging by printing the distances at each step, but the values seem to be correctly updated, just not leading to the correct path. My current environment is using .NET 5.0, and I'm running this code in a console application. I'm working on a web app that needs to handle this. How would you solve this? I'm working on a desktop app that needs to handle this. Could this be a known issue? Has anyone else encountered this? I'm working with C# in a Docker container on CentOS.