Post's correspondence problem

(classic problem)

Definition: Given a set of pairs of strings, find a sequence of pairs such that the concatenation of all first members of the pairs is the same string as the concatenation of all second members. This is an undecidable problem.

Also known as PCP.

Author: SKS

More information

Emil Post, A Variant of a Recursively Unsolvable Problem. Bulletin of the American Mathematical Society, 52:264-268, 1946.

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Entry modified 14 April 2009.
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Cite this as:
Sandeep Kumar Shukla, "Post's correspondence problem", in Dictionary of Algorithms and Data Structures [online], Vreda Pieterse and Paul E. Black, eds. 14 April 2009. (accessed TODAY) Available from: