**Reference**:- Erik D. Demaine, Martin L. Demaine, Yair N. Minsky, Joseph S. B. Mitchell, Ronald L. Rivest, and Mihai Pǎtraşcu, “Picture-Hanging Puzzles”, in
*Proceedings of the 6th International Conference on Fun with Algorithms (FUN 2012)*, Lecture Notes in Computer Science, Venice, Italy, June 4–6, 2012, pages 81–93. **Abstract**:-
We show how to hang a picture by wrapping rope around
*n*nails, making a polynomial number of twists, such that the picture falls whenever any*k*out of the*n*nails get removed, and the picture remains hanging when fewer than*k*nails get removed. This construction makes for some fun mathematical magic performances. More generally, we characterize the possible Boolean functions characterizing when the picture falls in terms of which nails get removed as all monotone Boolean functions. This construction requires an exponential number of twists in the worst case, but exponential complexity is almost always necessary for general functions. **Comments**:- The full paper is available as arXiv.org:1203.3602 of the Computing Research Repository (CoRR).
**Updates**:- Open Problem 1 was in fact previously solved by Gartside and Greenwood's paper "Brunnian links" (2007). The length of the shortest solution to the 1-out-of-
*n*puzzle is Θ(*n*^2); in fact, the exact bound matches the 2002 Chris Lusby Taylor construction we present. **Copyright**:- Copyright held by the authors.
**Length**:- The paper is 12 pages.
**Availability**:- The paper is available in PDF (583k).
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**Related papers**:- PictureHanging_TOCS (Picture-Hanging Puzzles)

See also other papers by Erik Demaine.

Last updated January 13, 2020 by Erik Demaine.