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  2. Kempner function - Wikipedia

    en.wikipedia.org/wiki/Kempner_function

    Graph of the Kempner function In number theory , the Kempner function S ( n ) {\displaystyle S(n)} [ 1 ] is defined for a given positive integer n {\displaystyle n} to be the smallest number s {\displaystyle s} such that n {\displaystyle n} divides the factorial s ! {\displaystyle s!} .

  3. Floor and ceiling functions - Wikipedia

    en.wikipedia.org/wiki/Floor_and_ceiling_functions

    In mathematics, the floor function is the function that takes as input a real number x, and gives as output the greatest integer less than or equal to x, denoted ⌊x⌋ or floor(x). Similarly, the ceiling function maps x to the least integer greater than or equal to x, denoted ⌈x⌉ or ceil(x). [1]

  4. Vertex cover - Wikipedia

    en.wikipedia.org/wiki/Vertex_cover

    Example graph that has a vertex cover comprising 2 vertices (bottom), but none with fewer. In graph theory, a vertex cover (sometimes node cover) of a graph is a set of vertices that includes at least one endpoint of every edge of the graph. In computer science, the problem of finding a minimum vertex cover is a classical optimization problem.

  5. Dijkstra's algorithm - Wikipedia

    en.wikipedia.org/wiki/Dijkstra's_algorithm

    However, specialized cases (such as bounded/integer weights, directed acyclic graphs etc.) can be improved further. If preprocessing is allowed, algorithms such as contraction hierarchies can be up to seven orders of magnitude faster. Dijkstra's algorithm is commonly used on graphs where the edge weights are positive integers or real numbers.

  6. Carmichael function - Wikipedia

    en.wikipedia.org/wiki/Carmichael_function

    Carmichael λ function: λ(n) for 1 ≤ n ≤ 1000 (compared to Euler φ function) In number theory, a branch of mathematics, the Carmichael function λ(n) of a positive integer n is the smallest positive integer m such that holds for every integer a coprime to n.

  7. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    Specifically, he considered functions of the form = + (), where a 0, b 0, ..., a P − 1, b P − 1 are rational numbers which are so chosen that g(n) is always an integer. The standard Collatz function is given by P = 2, a 0 = ⁠ 1 / 2 ⁠, b 0 = 0, a 1 = 3, b 1 = 1. Conway proved that the problem

  8. Adjacency matrix - Wikipedia

    en.wikipedia.org/wiki/Adjacency_matrix

    If n is the smallest nonnegative integer, such that for some i, j, the element (i, j) of A n is positive, then n is the distance between vertex i and vertex j. A great example of how this is useful is in counting the number of triangles in an undirected graph G , which is exactly the trace of A 3 divided by 3 or 6 depending on whether the graph ...

  9. Kruskal's algorithm - Wikipedia

    en.wikipedia.org/wiki/Kruskal's_algorithm

    For a graph with E edges and V vertices, Kruskal's algorithm can be shown to run in time O(E log E) time, with simple data structures. Here, O expresses the time in big O notation , and log is a logarithm to any base (since inside O -notation logarithms to all bases are equivalent, because they are the same up to a constant factor).