Tell us what’s happening:
I suggest updating step 54 of the curriculum. Currently, when inputting a string of nodes as the target, only one path is processed at a time, which i don’t think is the intended behavior. If ‘BD’ is entered as the target, it should show paths to both ‘B’ and ‘D’, but the code breaks. A possible improvement is changing [target] to list(target), allowing the string to split into individual nodes correctly.
Your code so far
my_graph = {
'A': [('B', 3), ('D', 1)],
'B': [('A', 3), ('C', 4)],
'C': [('B', 4), ('D', 7)],
'D': [('A', 1), ('C', 7)]
}
def shortest_path(graph, start, target = ''):
unvisited = list(graph)
distances = {node: 0 if node == start else float('inf') for node in graph}
paths = {node: [] for node in graph}
paths[start].append(start)
while unvisited:
current = min(unvisited, key=distances.get)
for node, distance in graph[current]:
if distance + distances[current] < distances[node]:
distances[node] = distance + distances[current]
if paths[node] and paths[node][-1] == node:
paths[node] = paths[current][:]
else:
paths[node].extend(paths[current])
paths[node].append(node)
unvisited.remove(current)
# User Editable Region
targets_to_print = [target] if target else graph
shortest_path(my_graph, 'A')
# User Editable Region
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Challenge Information:
Learn Algorithm Design by Building a Shortest Path Algorithm - Step 55