Issues with Dijkstra's Algorithm Implementation in Python - Incorrect Shortest Path Calculation
I'm trying to implement I'm refactoring my project and I'm testing a new approach and I can't seem to get I'm stuck on something that should probably be simple... I'm currently working on a project that requires finding the shortest path in a weighted graph using Dijkstra's algorithm, but I'm encountering some unexpected behavior. My implementation seems to return incorrect paths when the graph contains nodes with the same weight. Here's a simplified version of my code: ```python import heapq class Graph: def __init__(self): self.edges = {} def add_edge(self, from_node, to_node, weight): if from_node not in self.edges: self.edges[from_node] = [] self.edges[from_node].append((to_node, weight)) def dijkstra(self, start): queue = [(0, start)] # (cost, node) distances = {start: 0} while queue: current_distance, current_node = heapq.heappop(queue) if current_distance > distances.get(current_node, float('inf')): continue for neighbor, weight in self.edges.get(current_node, []): distance = current_distance + weight if distance < distances.get(neighbor, float('inf')): distances[neighbor] = distance heapq.heappush(queue, (distance, neighbor)) return distances # Example usage: g = Graph() g.add_edge('A', 'B', 1) g.add_edge('A', 'C', 1) g.add_edge('B', 'D', 1) g.add_edge('C', 'D', 2) result = g.dijkstra('A') print(result) # Expecting {'A': 0, 'B': 1, 'C': 1, 'D': 2} ``` In this example, I am adding edges between nodes A, B, C, and D with weights. However, I noticed that when I try to find the shortest path from A to D, I sometimes get an incorrect distance, such as 3 instead of the expected 2. I've checked my edge weights and the graph structure multiple times. It seems to happen consistently when I have multiple paths to a node with the same cumulative weight. Are there any known issues or common pitfalls with Dijkstra’s algorithm that I might be overlooking? I would appreciate any insights or suggestions for debugging this issue. I'd really appreciate any guidance on this. The stack includes Python and several other technologies. I'd love to hear your thoughts on this. I'd really appreciate any guidance on this. This is happening in both development and production on Debian. I'm open to any suggestions. This is for a REST API running on CentOS.