15. NP-Completeness

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MIT 18.404J Theory of Computation, Fall 2020
Instructor: Michael Sipser

Quickly reviewed last lecture. Covered NP-completeness; SAT and 3SAT; and more. Discussed a strategy for proving NP-completeness with a reduction from 3SAT by constructing gadgets that simulate variables and clauses.

License: Creative Commons BY-NC-SA

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Probably my favourite lecture up until now!!

MayankGoel
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Just for clarity, for the 3SAT to CLIQUE conversion, the vertices of the graph are not the unique literals themselves, but rather for each clause in the formula there must be one vertex for each one of its literals. So formally, the vertices can be seen as ordered pairs (n, X), where n indicates a clause of the formula and X indicates one of its literals. Then the construction is that vertices (n, X) and (m, Y) are connected by an edge if and only if n≠m and the truth of X is consistent with the truth of Y.

connorfrankston
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yay, i like that you mention the similarity between the symbols of reunion/disjunction and intersetion/conjunction

florianvanbondoc
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Something that helps me remember the difference between the And and the Or symbols is the And looks kinda like an A

vyliad
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What's the difference between verify and test? Seems to me they are not quite different...

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