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Python implementation of Dijkstra's Algorithm
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from collections import defaultdict | |
class Graph: | |
def __init__(self): | |
self.nodes = set() | |
self.edges = defaultdict(list) | |
self.distances = {} | |
def add_node(self, value): | |
self.nodes.add(value) | |
def add_edge(self, from_node, to_node, distance): | |
self.edges[from_node].append(to_node) | |
self.edges[to_node].append(from_node) | |
self.distances[(from_node, to_node)] = distance | |
def dijsktra(graph, initial): | |
visited = {initial: 0} | |
path = {} | |
nodes = set(graph.nodes) | |
while nodes: | |
min_node = None | |
for node in nodes: | |
if node in visited: | |
if min_node is None: | |
min_node = node | |
elif visited[node] < visited[min_node]: | |
min_node = node | |
if min_node is None: | |
break | |
nodes.remove(min_node) | |
current_weight = visited[min_node] | |
for edge in graph.edges[min_node]: | |
key = (min_node, edge) | |
if key in graph.distances: | |
weight = current_weight + graph.distances[key] | |
if edge not in visited or weight < visited[edge]: | |
visited[edge] = weight | |
path[edge] = min_node | |
return visited, path |
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