FACTOID # 151: The five countries with the highest coffee consumption are also the five countries whose citizens trust one another the most. Coincidence? Probably.
 
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Encyclopedia > Disjoint sets

In mathematics, two sets are said to be disjoint if they have no element in common. For example, {1, 2, 3} and {4, 5, 6} are disjoint sets. Wikibooks Wikiversity has more about this subject: School of Mathematics Wikiquote has a collection of quotations by or about: Mathematics Look up Mathematics in Wiktionary, the free dictionary Wikimedia Commons has more media related to: Mathematics Bogomolny, Alexander: Interactive Mathematics Miscellany and Puzzles. ... In mathematics, a set can be thought of as any well-defined collection of things considered as a whole. ... In mathematics, an element (also called a member) is an object contained in a set (or more generally a class). ...


Formally, two sets A and B are disjoint if their intersection is the empty set, i.e. if In mathematics, the intersection of two sets A and B is the set that contains all elements of A that also belong to B (or equivalently, all elements of B that also belong to A), but no other elements. ... In mathematics, the empty set is the set with no elements. ...

This definition extends to any collection of sets. A collection of sets is pairwise disjoint or mutually disjoint if any two distinct sets in the collection are disjoint.


Formally, let I be an index set, and for each i in I, let Ai be a set. Then the family of sets {Ai : iI} is pairwise disjoint if for any i and j in I with ij, In mathematics, an index set is another name for a function domain. ...

For example, the collection of sets { {1}, {2}, {3}, ... } is pairwise disjoint. If {Ai} is a pairwise disjoint collection, then clearly its intersection is empty:

However, the converse is not true: the intersection of the collection {{1, 2, 3}, {4, 5, 6}, {3, 4}} is empty, but the collection is not pairwise disjoint.


A partition of a set X is any collection of non-empty subsets {Ai : iI} of X such that {Ai} are pairwise disjoint and A partition of U into 6 blocks: a Venn diagram representation. ...

See also


  Results from FactBites:
 
Class notes CS251B -- Winter 1997 (1992 words)
Disjoint sets structures are yet another new abstract data type (A.D.T.) for which we must now define a mathematical model and a series of related operations.
Disjoint sets, sometimes called partitions, are the model of this A.D.T. A partition is a collection of disjoint sets such that the union of the sets is the entire space.
The data structure used is disjoint set forests with contribution from the path compression heuristic.
Disjoint sets - Wikipedia, the free encyclopedia (204 words)
In mathematics, two sets are said to be disjoint if they have no element in common.
For example, {1, 2, 3} and {4, 5, 6} are disjoint sets.
Formally, two sets A and B are disjoint if their intersection is the empty set, i.e.
  More results at FactBites »


 

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