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In graph theory, a branch of combinatorial mathematics, a block graph or clique tree [1] is a type of undirected graph in which every biconnected component (block) is a clique. Block graphs are sometimes erroneously called Husimi trees (after Kôdi Husimi ), [ 2 ] but that name more properly refers to cactus graphs , graphs in which every ...
Switching {X,Y} in a graph. A two-graph is equivalent to a switching class of graphs and also to a (signed) switching class of signed complete graphs.. Switching a set of vertices in a (simple) graph means reversing the adjacencies of each pair of vertices, one in the set and the other not in the set: thus the edge set is changed so that an adjacent pair becomes nonadjacent and a nonadjacent ...
Every edge of a graph belongs in exactly one block. 2. The block graph of a graph G is another graph whose vertices are the blocks of G, with an edge connecting two vertices when the corresponding blocks share an articulation point; that is, it is the intersection graph of the blocks of G. The block graph of any graph is a forest. 3.
The building blocks are usually sold in building block sets with building instructions, less often as single-variety or mixed bulk. In addition to the main model of a set, building instructions for an alternative model ("B-model") are occasionally included, often advertised as such ("2-in-1", "3-in-1").
The star graphs K 1,3, K 1,4, K 1,5, and K 1,6. A complete bipartite graph of K 4,7 showing that Turán's brick factory problem with 4 storage sites (yellow spots) and 7 kilns (blue spots) requires 18 crossings (red dots) For any k, K 1,k is called a star. [2] All complete bipartite graphs which are trees are stars. The graph K 1,3 is called a ...
The line graphs of bipartite graphs form one of the key building blocks of perfect graphs, used in the proof of the strong perfect graph theorem. [15] A special case of these graphs are the rook's graphs, line graphs of complete bipartite graphs. Like the line graphs of complete graphs, they can be characterized with one exception by their ...
In one form of block scheduling, a single class will meet every day for a number of days, after which another class will take its place. In another form, daily classes rotate through a changing daily cycle. [1] Blocks offer more concentrated experiences of subjects, with fewer, usually half as many if going through a schedule transfer, classes ...
KEVA Planks is a wooden block construction toy. Froebel gifts are a range of educational materials first used in the original Kindergarten. Montessori sensorial materials are a range of educational materials including wooden blocks. Pattern blocks and Cuisenaire rods are sets of small blocks used in mathematics education and also in block play.