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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 \(L\)?
अब तपाईँ कुनै गणकयन्त्रले यो एकलाई समाधान गर्दैन, तर यसको टुक्राहरू गणनायोग्य छन् । तल एउटा प्रयास गर्नुहोस्, वा तपाईँको आफ्नै टाइप गर्नुहोस् ।
एक निःशुल्क खाता प्रत्येक पाठ मा नोट थप्छ, तपाईं के समाप्त गरेको छ को एक रेकर्ड, एक ठाउँमा आफ्नो समाधान समस्या, र एक शिक्षक तपाईं यो पृष्ठ बारेमा सोध्न सक्नुहुन्छ. गणित आफैलाई सबैलाई खुला छ, मा साइन इन वा छैन.
साइन अप गर्नुहोस् लगइनयहाँ प्रयोग गरिएको प्रतीक
पूर्ण परिभाषा, एउटा तस्वीर, र यो प्रत्येक अक्षर अर्थ के लागि कुनै पनि प्रतीक ट्याप गर्नुहोस्।
प्रश्नहरू मानिसहरूले सोध्छन्
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.
यो पृष्ठको भागहरू यसबाट अनुकूलित गरिएको छ Keller & Trotter, Applied Combinatorics (CC BY-SA 4.0). यहाँको मुख्य पेशा कृषि र पशुपालन हो।
यसमा थप 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