List questions from extremal-combinatorics

Published on 15 Apr 2026 - 9:18

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Students who see ears of another student

Published on 09 Apr 2026 - 7:08

219

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No sum of three numbers equals another number in set

Published on 11 Apr 2026 - 2:12

85

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Union of each family is not the whole set

Published on 11 Apr 2026 - 4:55

88

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How find the smallest $m$ such this $|A|=n,|B|=m,A\subseteq B$

Published on 17 Apr 2026 - 11:24

281

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Minimum number of circles with 3 neighbors

Published on 14 Apr 2026 - 0:58

320

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Say $E_1,...E_n\subset\{1,2,...,k\}= K$, each $|E_i|=4$ and each $j\in K$ appear in at most $3$ sets $E_i$.

Published on 11 May 2026 - 1:09

167

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A class of 46 form groups each of which contains exactly three members so that any two groups have at most one member in common. Prove that...

Published on 11 May 2026 - 1:13

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Generate all different available combinations

Published on 25 Mar 2026 - 20:39

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Two families with odd intersections of their sets

Published on 25 Mar 2026 - 23:37

92

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$S = \{1,2,3,...,2018\}$ and $M \subseteq S$, $\forall \{x,y,z\} \subseteq M, \: xy \ne z$. What is the maximum possible value for $|M|$

Published on 25 Mar 2026 - 23:42

66

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Prove that the size of a graph is at most $16$

Published on 10 May 2026 - 16:12

31

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What is the minimal number of vertices a graph not distance-embeddable in $\mathbb{R}^n$ can have?

Published on 25 Mar 2026 - 20:36

164

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What's an easy algorithm to check for triangle-freeness?

Published on 25 Mar 2026 - 20:34

60

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How to interpret the intuitive idea behind Szemerédi regularity lemma?

Published on 10 May 2026 - 17:13

List Question

Chips do not form rectangle on board

Students who see ears of another student

No sum of three numbers equals another number in set

Union of each family is not the whole set

How find the smallest $m$ such this $|A|=n,|B|=m,A\subseteq B$

Minimum number of circles with 3 neighbors

Say $E_1,...E_n\subset\{1,2,...,k\}= K$, each $|E_i|=4$ and each $j\in K$ appear in at most $3$ sets $E_i$.

A class of 46 form groups each of which contains exactly three members so that any two groups have at most one member in common. Prove that...

Generate all different available combinations

Two families with odd intersections of their sets

$S = \{1,2,3,...,2018\}$ and $M \subseteq S$, $\forall \{x,y,z\} \subseteq M, \: xy \ne z$. What is the maximum possible value for $|M|$

Prove that the size of a graph is at most $16$

What is the minimal number of vertices a graph not distance-embeddable in $\mathbb{R}^n$ can have?

What's an easy algorithm to check for triangle-freeness?

How to interpret the intuitive idea behind Szemerédi regularity lemma?

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