# What Is Transitive and Reflexive Transitive Closure in Data Structure?

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Heather Bennett

What Is Transitive and Reflexive Transitive Closure in Data Structure?

In the field of data structures, the concepts of transitive closure and reflexive transitive closure play a crucial role. These concepts help in understanding and analyzing relationships between elements in a set or graph. Let’s delve deeper into what transitive closure and reflexive transitive closure mean.

## Transitive Closure

The transitive closure of a relation R on a set A is defined as the smallest relation R’ that satisfies the following condition:

If (a,b) ∈ R’ and (b,c) ∈ R’, then (a,c) ∈ R’

In simpler terms, the transitive closure of a relation includes all possible indirect relationships that can be inferred from the direct relationships in the original relation. It helps in determining if there is a path between any two elements in a set.

### Example:

Consider a set A = {1, 2, 3} with a relation R = {(1, 2), (2, 3)}. The transitive closure of R, denoted as R*, would include additional pairs such as (1, 3) since it completes the indirect relationship through (1, 2) and (2, 3).

## Reflexive Transitive Closure

The reflexive transitive closure extends on the concept of transitive closure by also including reflexive relationships. A reflexive relationship is one where each element is related to itself.

The reflexive transitive closure of a relation R on a set A is defined as the smallest relation R’ that satisfies both the conditions:

1. If (a,b) ∈ R’, then (a,c) ∈ R’ for any element c in A.
2. (a,a) ∈ R’ for all elements a in A.

The reflexive transitive closure ensures that not only indirect relationships are considered but also each element is related to itself.

Considering the same set A = {1, 2, 3} with the relation R = {(1, 2), (2, 3)}, the reflexive transitive closure of R, denoted as R+, would include additional pairs such as (1, 1), (2, 2), and (3, 3) to satisfy the reflexive condition.

To summarize, transitive closure and reflexive transitive closure help in analyzing relationships within a set or graph. The former includes all indirect relationships inferred from direct relationships, while the latter includes both indirect relationships and reflexive relationships. Understanding these concepts is essential when studying data structures and their applications.