Unexpected Behavior in Dijkstra's Algorithm with Negative Edge Weights in Python
I'm updating my dependencies and I've been banging my head against this for hours. I'm currently implementing Dijkstra's algorithm to find the shortest path in a graph represented with an adjacency list in Python. However, I'm running into unexpected behavior when I include negative edge weights. I expected Dijkstra's algorithm to handle only non-negative weights, but I'm not sure how to manage cases where these weights appear in my graph. My implementation returns a wrong path and an unexpected distance value. Here's a snippet of my code: ```python import heapq from collections import defaultdict class Graph: def __init__(self): self.graph = defaultdict(list) def add_edge(self, u, v, weight): self.graph[u].append((v, weight)) def dijkstra(self, start): distances = {node: float('inf') for node in self.graph} distances[start] = 0 priority_queue = [(0, start)] # (distance, node) while priority_queue: current_distance, current_node = heapq.heappop(priority_queue) if current_distance > distances[current_node]: continue for neighbor, weight in self.graph[current_node]: distance = current_distance + weight if distance < distances[neighbor]: distances[neighbor] = distance heapq.heappush(priority_queue, (distance, neighbor)) return distances # Creating the graph and adding edges with negative weight g = Graph() g.add_edge('A', 'B', 4) g.add_edge('A', 'C', 1) g.add_edge('C', 'B', -2) g.add_edge('B', 'D', 2) g.add_edge('C', 'D', 5) distances = g.dijkstra('A') print(distances) # Expecting {'A': 0, 'B': 2, 'C': 1, 'D': 4} but getting wrong results ``` In this example, I'm adding a negative edge from C to B. I would expect Dijkstra's algorithm to correctly compute the shortest distance, but instead, it seems to fail and returns incorrect distances for nodes. Is there a recommended approach to handle graphs with negative weights, or do I need to switch to a different algorithm like Bellman-Ford? Any insights or improvements to my current approach would be greatly appreciated! Any help would be greatly appreciated! This is part of a larger microservice I'm building. Any advice would be much appreciated.