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### Does two languages being in P imply reduction to each other?

Given two languages $L_1$ and $L_2$ that are in $\mathsf{P}$, can it be proven that there is a polynomial time reduction from $L_1$ to $L_2$ and vice versa? If so, how? I noticed that if $L_1$ is the ...
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### determine Eulerian or Hamiltonian

I am a beginner in graph theory and just found this question in a book after completing few topics and I was wondering how you approach this questions. For eulerian, I can say that the graph has ...
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### Why don't passwords prove P != NP?

Pardon my ignorance on the matter but, Verifying passwords = Polynomial (linear) Guessing passwords = Exponential Since each guess has nothing to do with one another, exponential time is best possible ...
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### Is it necessary for NP problems to be decision problems?

Professor Tim Roughgarden from Stanford University while teaching a MOOC said that solutions to problems in the class NP must be polynomial in length. But the wikipedia article says that NP problems ...
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### P vs NP and Angle Trisection (serious question)

I have a question. Please be nice; I come from the corporate world and my knowledge of computer theory is around a college freshman level. My understanding from many popular-level sources (like Scott ...
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### Is P contained in NP-hard?

I'm studying complexity classes and the diagram in NP-Hardness article is confusing to me. NP-hard has all problems that can be reduced in polynomial time from a problem in NP to them. P is contained ...