Added Kruskal's Algorithm (more organized than the one present) #2218
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ruppysuppy
commented
Jul 21, 2020
| # create a new set with x as its member | ||
| self.map[x] = Disjoint_Set_Tree_Node(x) | ||
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| def find_set(self, x): | ||
| def find_set(self, x: int) -> Disjoint_Set_Tree_Node: |
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Missed the type hints in a few places, will add them
|
Could you review the PR please, @cclauss? |
swapnanildutta
approved these changes
Aug 11, 2020
cclauss
reviewed
Aug 11, 2020
Comment on lines
24
to
26
| if self.map[x] != self.map[x].parent: | ||
| self.map[x].parent = self.find_set(self.map[x].parent.key) | ||
| return self.map[x].parent |
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Suggested change
| if self.map[x] != self.map[x].parent: | |
| self.map[x].parent = self.find_set(self.map[x].parent.key) | |
| return self.map[x].parent | |
| self_map_x = self.map[x] | |
| if self_map_x != self_map_x.parent: | |
| self_map_x.parent = self.find_set(self_map_x.parent.key) | |
| return self_map_x.parent |
OPTIONAL: You might gain a bit of performance...
https://wiki.python.org/moin/PythonSpeed/PerformanceTips#Loops
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I'm keeping it as list comprehension, converting
[disjoint_set.make_set(node) for node in self.connections]to
map(disjoint_set.make_set, self.connections.keys())yields:
**********************************************************************
File "d:/Desktop/Projects/GitUploads/Python/graphs/minimum_spanning_tree_kruskal2.py", line 77, in __main__.GraphUndirectedWeighted.kruskal
Failed example:
mst = graph.kruskal()
Exception raised:
Traceback (most recent call last):
File "C:\Program Files\Python37\lib\doctest.py", line 1329, in __run
compileflags, 1), test.globs)
File "<doctest __main__.GraphUndirectedWeighted.kruskal[7]>", line 1, in <module>
mst = graph.kruskal()
File "d:/Desktop/Projects/GitUploads/Python/graphs/minimum_spanning_tree_kruskal2.py", line 100, in kruskal
parentu = disjoint_set.find_set(u)
File "d:/Desktop/Projects/GitUploads/Python/graphs/minimum_spanning_tree_kruskal2.py", line 24, in find_set
elem_ref = self.map[x]
KeyError: 1
**********************************************************************
File "d:/Desktop/Projects/GitUploads/Python/graphs/minimum_spanning_tree_kruskal2.py", line 78, in __main__.GraphUndirectedWeighted.kruskal
Failed example:
assert 5 not in mst.connections[3]
Exception raised:
Traceback (most recent call last):
File "C:\Program Files\Python37\lib\doctest.py", line 1329, in __run
compileflags, 1), test.globs)
File "<doctest __main__.GraphUndirectedWeighted.kruskal[8]>", line 1, in <module>
assert 5 not in mst.connections[3]
NameError: name 'mst' is not defined
**********************************************************************
1 items had failures:
2 of 9 in __main__.GraphUndirectedWeighted.kruskal
***Test Failed*** 2 failures.
ruppysuppy
commented
Aug 12, 2020
cclauss
reviewed
Aug 12, 2020
| # add a node ONLY if its not present in the graph | ||
| if node not in self.connections: | ||
| self.connections[node] = {} | ||
| self.nodes += 1 |
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Under what circumstances is self.nodes != len(self.connections)?
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Yeah its always same. Should I remove it?
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Your call. You already have my approval so you can squash & merge whenever you want (as long as the tests are green). Well done!
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I have made the changes, but I cannot merge since I'm not a member
stokhos
pushed a commit
to stokhos/Python
that referenced
this pull request
Jan 3, 2021
…lgorithms#2218) * Added Kruskal's Algorithm * Added Type Hints * fixup! Format Python code with psf/black push * Added Type Hints V2 * Implemented suggestions + uniform naming convention * removed redundant variable (self.nodes) * updating DIRECTORY.md Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
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Checklist:
Fixes: #{$ISSUE_NO}.