👀 Views: 4 💬 Answers: 1 📅 Created: 2025-06-05

python algorithms dijkstra Python

I've spent hours debugging this and I'm relatively new to this, so bear with me. I tried several approaches but none seem to work. I'm stuck on something that should probably be simple. I'm currently implementing Dijkstra's algorithm in Python 3.10 to find the shortest path in a weighted graph. However, I'm working with an scenario where the distances to some nodes are not updating correctly, leading to incorrect shortest path calculations. Here’s a simplified version of my implementation: ```python import heapq from collections import defaultdict class Graph: def __init__(self): self.edges = defaultdict(list) def add_edge(self, from_node, to_node, weight): self.edges[from_node].append((to_node, weight)) def dijkstra(self, start): queue = [(0, start)] # (distance, node) distances = {node: float('inf') for node in self.edges} distances[start] = 0 visited = set() while queue: current_distance, current_node = heapq.heappop(queue) if current_node in visited: continue visited.add(current_node) for neighbor, weight in self.edges[current_node]: distance = current_distance + weight if distance < distances[neighbor]: distances[neighbor] = distance heapq.heappush(queue, (distance, neighbor)) return distances # Example usage graph = Graph() graph.add_edge('A', 'B', 1) graph.add_edge('A', 'C', 4) graph.add_edge('B', 'C', 2) graph.add_edge('B', 'D', 5) graph.add_edge('C', 'D', 1) print(graph.dijkstra('A')) # Expected: {'A': 0, 'B': 1, 'C': 3, 'D': 4} ``` However, when I run this code, I get unexpected distances for some of the nodes, particularly for node 'C'. My output shows: ``` {'A': 0, 'B': 1, 'C': 5, 'D': 4} ``` It seems like the distance to 'C' is being calculated incorrectly. I've double-checked the edge weights and ensured that all nodes are being added correctly. I've also tried different graph configurations, but I need to seem to find the root cause of this scenario. Any insights or suggestions on what I might be missing? For context: I'm using Python on Linux. Any ideas what could be causing this? I'm working on a CLI tool that needs to handle this. This is part of a larger CLI tool I'm building. Thanks for taking the time to read this!