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DisjointSetsPathCompression possible bug #19

Description

@justinblaber

This line of code:

item, self._parent[item] = parent, self._parent[parent]

The problem is this:

parents = [1, 2, 2]
item = 0
parent = parents[item]
item, parents[item] = parent, parents[parent]
print(parents)

prints [1, 2, 2]

But 0's parent should be 2 now.

If you separate them out and do:

parents = [1, 2, 2]
item = 0
parent = parents[item]
parents[item] = parents[parent]
item = parent
print(parents)

This correctly prints [2, 2, 2].

This seems like some complex order of operations issue with multiple assignment in python. I'm using 3.8.8.

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