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Questions tagged [post-correspondence]

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Post correspondence problem for finite monoids

The Post correspondence problem has the following version for finite monoids: Input: a finite monoid $M$ and a finite list $(m_1,m_1'),\ldots, (m_n,m_n')$ of pairs of elements of $M$ Question: is ...
2 votes
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Post Correspondence Problem "binary" variant

Bounded Post Correspondence Problem is defined as follows: given list of pairs of words $ (x_1,y_1), \ldots, (x_n, y_n) $ and $K$ find sequence of indexes $i_1, \ldots, i_k$, $k \leq K$ so that $x_{...
-2 votes
1 answer

A variant of the Post Correspondence problem

Given words $\alpha_1, \ldots \alpha_n$ and $\beta_1, \ldots, \beta_n$, Post's Correspondence Problem asks if there is a sequence $i_1, \ldots, i_k$ of indices such that $\alpha_{i_1} \ldots \alpha_{...
1 vote
2 answers

Are equalizers of regular functions always regular languages? (My guess is no because PCP, but...)

Edit: I originally defined a regular function as a function computable by a Mealy machine, but Denis pointed out that that was a weaker model than what I was thinking of. So to be more precise, by a "...
5 votes
0 answers

Bounded Post Correspondence Problem NP-Complete Proof

I'm looking for a simple proof that shows that the Bounded-PCP problem belongs to NP-Complete as many text books say so. It is clear to me that the problem is decidable but I cannot find any reduction ...
5 votes
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Prove Post Correspondence Problem Non-Recursive Without Reduction

Given a set of pairs of words $P = \{(\alpha_1, \beta_1), \dots, (\alpha_n, \beta_n)\} \subseteq \Sigma^*\times\Sigma^*$, the Post Correspondence Problem (PCP) is to decide wether or not there are ...