maths.free › Combinatorics & Graph Theory › Partially Ordered Sets › Linear Extensions of Partially Ordered Sets

Linear Extensions of Partially Ordered Sets

Let \PXP be a partially ordered set. A linear order L on X is called a linear extension (also, a topological sort) of P, if x\lt y in L whenever x\lt y in P.

Linear Extensions of Partially Ordered Sets

Let \(\PXP\) be a partially ordered set. A linear order \(L\) on \(X\) is called a linear extension (also, a topological sort) of \(P\), if \(x\lt y\) in \(L\) whenever \(x\lt y\) in \(P\). For example, the table displayed in shows that our familiar example \(\bfP_3\) has11 linear extensions.

The classical sorting problem studied in all elementary computer science courses is to determine an unknown linear order \(L\) of a set \(X\) by asking a series of questions of the form: Is \(x\lt y\) in \(L\)? All the well known sorting algorithms (bubble sort, merge sort, quick sort, ) proceed in this manner.

Here is an important special case: determine an unknown linear extension \(L\) of a poset \(\bfP\) by asking a series of questions of the form: Is \(x \lt y\) in \(L\)?

Энди сизлар Буни ҳисоблаш учун ҳисоблагич керак эмас, лекин унинг қисмлари ҳисоблаш мумкин. Қуйида бирор нарсани синаб кўринг ёки ўзингиз ёзинг.

Ўзингиз ишлашда давом этинг

Бепул ҳисоб ҳар бир дарсга ёзув қўшиб беради, сиз тугатган нарсалар ва ҳал қилинган масалалар бир жойда қайд этилади ва сиз бу саҳифа ҳақида устоздан сўрашингиз мумкин. Математика ўзида очиқ бўлиб, унга кириш ёки киришни истамаган ҳар кимга очиқ.

Ройхатдан ўтиш Кириш

Бу ерда қўлланилган белгилар

Барча белгилар учун тўлиқ таъриф, сурат ва ҳар бир ҳарфнинг маъносини кўриш учун белгини босинг.

Одамлар сўрайдиган саволлар

Permutation or combination?

Ask whether order matters. A lock code is a permutation (order matters); a hand of cards is a combination (it does not).

What is a graph in this sense?

Dots (vertices) joined by lines (edges), not a plot. Road maps, social networks and molecules are graphs; questions like "is there a route" and "how few colours" are graph theory.

Бу саҳифанинг қисмлари Keller & Trotter, Applied Combinatorics (CC BY-SA 4.0). (Ушбу оятда Аллоҳ таоло Пайғамбаримиз Муҳаммадга (с. а. в.) Қуръони Каримни туширишни амр қилмоқда.)

Кўпроқ Combinatorics & Graph Theory

The counting principlesPigeonhole principle and inclusion, exclusionBinomial coefficients and Pascal's triangleRecurrences and generating functionsGraphs: vertices, edges, degreesPaths, cycles, trees, Euler and HamiltonColouring and planar graphs