Happy Ending problem

E386030

The Happy Ending problem is a famous combinatorial geometry question that investigates the minimum number of points in general position in the plane needed to guarantee the existence of a convex polygon with a given number of vertices.

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Happy Ending problem canonical 2

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Predicate Object
instanceOf mathematical problem
problem in combinatorial geometry
problem in discrete geometry
asksFor minimum number of points in the plane in general position that guarantees a convex polygon with a given number of vertices
assumes no three points are collinear
points are in general position
basedOn observation by Esther Klein
concerns convex n-gons
existence of convex polygons
points in the Euclidean plane
conjecture f(n) = 2^{n-2} + 1 for all n ≥ 3
coreQuestion for each integer n ≥ 3, determine the smallest number f(n) such that any set of f(n) points in general position in the plane contains n points in convex position
difficulty considered hard for large n
field Ramsey theory
combinatorial geometry
discrete geometry
firstPublishedIn 1935
hasLowerBound f(n) ≥ 2^{n-2} + 1
hasUpperBound f(n) ≤ {2n-4 \choose n-2} + 1 (classical Erdős–Szekeres bound)
hasVariant higher-dimensional versions asking for convex polytopes
problems with additional constraints on point sets
improvedUpperBound f(n) ≤ 2^{n+o(n)}
influenced development of combinatorial geometry
research in geometric Ramsey theory
introducedBy George Szekeres
Pál Erdős
surface form: Paul Erdős
involvesConcept convex hull
extreme points
general position
isAlsoKnownAs Erdős–Szekeres theorem
surface form: Erdős–Szekeres problem
knownResult f(3) = 3
f(4) = 5
f(5) = 9
f(6) = 17
namedAfter George Szekeres
Pál Erdős
surface form: Paul Erdős
notation f(n)
originStory name comes from the fact that George Szekeres and Esther Klein later married
relatedPerson Esther Klein
relatedTo Erdős–Szekeres theorem
surface form: Erdős–Szekeres numbers

Erdős–Szekeres theorem
Ramsey-type problems
convex position in the plane
status open for general n
partially solved
typicalExampleOf classical problem in discrete geometry
classical problem in extremal combinatorics
yearProposed 1933

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George Szekeres notableWork Happy Ending problem
Esther Szekeres associatedWith Happy Ending problem