Download presentation

Presentation is loading. Please wait.

Published byBryce Belcourt Modified over 3 years ago

1
Post Correspondence Problem [Section 5.2] Suppose we have dominos of strings, e.g.: The question: is it possible to arrange the dominos in line (repetitions of dominos are allowed) in such a way so that the top forms the same string as the bottom? b ca abc c ca a a ab

2
Post Correspondence Problem [Section 5.2] Formally, given is a collection P of dominos: P = { (t 1,b 1 ), (t 2,b 2 ), …, t k,b k ) } A match is a sequence i 1,i 2,…,i s, where t i1 t i2 …t is = b i1 b i2 …b is. The Post Correspondence Problem (PCP) asks if there is a match for P. Thm 5.15: PCP is undecidable.

3
Post Correspondence Problem [Section 5.2] First, we’ll consider MPCP where we are looking for instances that have a match that starts with the first domino. MPCP = { | P = { (t 1,b 1 ), (t 2,b 2 ), …, t k,b k ) } is a PCP that has match starting with (t_1,b_1) } Claim: PCP is equivalent to MPCP.

4
Post Correspondence Problem [Section 5.2] Thm 5.15: PCP is undecidable.

5
Post Correspondence Problem [Section 5.2] Thm: Ambiguity of CFGs is undecidable.

Similar presentations

OK

Computability and Complexity 7-1 Computability and Complexity Andrei Bulatov Recursion Theorem.

Computability and Complexity 7-1 Computability and Complexity Andrei Bulatov Recursion Theorem.

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on event driven programming advantages Ppt on marketing management process Ppt on depth first search Ppt on limits and continuity ap Ppt on pf and esi Ppt on blind stick with sensors Ppt on nitrogen cycle and nitrogen fixation is a process Ppt on management by objectives method Ppt on uniqueness of indian culture Ppt on architectural heritage of india