Update Dijkstra's to use set #10
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Takashiidobe
commented
Mar 27, 2024
| @@ -18,27 +17,25 @@ def make_graph(): | |||
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| def dijkstras_heap(G, start='A'): | |||
| shortest_paths = {} | |||
| visited = {} | |||
| visited = set() | |||
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This one is the change noted in the issue about representing the set as a dict when a set would do.
Takashiidobe
commented
Mar 27, 2024
| heap = [] | ||
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| for node in list(G.keys()): | ||
| for node in G.keys(): |
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G.keys() is an iterator, so there's no need to turn it into a list.
| @@ -47,7 +44,7 @@ def dijkstras_heap(G, start='A'): | |||
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| def dijkstras(G, start='A'): | |||
| shortest_paths = {} | |||
| unvisited = list(G.keys()) | |||
| unvisited = dict.fromkeys(G.keys()) | |||
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The code used to be a list, which would then call remove on min_node in a loop. There's no guarantee that min_node is at the end of the list, so remove has to do a seek to find the min_node in the list and remove it, and both operations are O(n).
If it's changed to a dictionary, finding the min_node is O(1) and removing it is also O(1).
msambol
reviewed
Mar 27, 2024
msambol
reviewed
Mar 27, 2024
msambol
requested changes
Mar 27, 2024
msambol
changed the title
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Some changes reviewing the dijkstra's shortest path algo
ref: #9