## What is the condition for planarity?

## What is the condition for planarity?

A graph G= (V, E) is said to be planar if it can be drawn in the plane so that no two edges of G intersect at a point other than a vertex. Such a drawing of a planar graph is called a planar embedding of the graph.

**How do you know if a bipartite graph is planar?**

A bipartite graph is planar iff it has no K3,3 or K5 minors….These are drawings satisfying:

- All vertices of one part are drawn on a single vertical line.
- Edges do not intersect except at vertices.

**What is planarity of a graph?**

Planarity – “A graph is said to be planar if it can be drawn on a plane without any edges crossing. Such a drawing is called a planar representation of the graph.” Important Note – A graph may be planar even if it is drawn with crossings, because it may be possible to draw it in a different way without crossings.

### Can a bipartite graph be planar?

Every planar graph whose faces all have even length is bipartite. Special cases of this are grid graphs and squaregraphs, in which every inner face consists of 4 edges and every inner vertex has four or more neighbors.

**How we can use kuratowski’s theorem to detect whether a graph is planar or not?**

Kuratowski subgraphs If G is a graph that contains a subgraph H that is a subdivision of K5 or K3,3, then H is known as a Kuratowski subgraph of G. With this notation, Kuratowski’s theorem can be expressed succinctly: a graph is planar if and only if it does not have a Kuratowski subgraph.

**Is K3 4 a planar?**

The authors previously published an iterative process to generate a class of projective- planar K3,4-free graphs called ‘patch graphs’. They also showed that any simple, almost 4-connected, nonplanar, and projective-planar graph that is K3,4-free is a subgraph of a patch graph.

#### Why is K5 not planar?

K5: K5 has 5 vertices and 10 edges, and thus by Lemma 2 it is not planar. K3,3: K3,3 has 6 vertices and 9 edges, and so we cannot apply Lemma 2.

**Is K3 planar?**

K3,3: K3,3 has 6 vertices and 9 edges, and so we cannot apply Lemma 2. But notice that it is bipartite, and thus it has no cycles of length 3. We may apply Lemma 4 with g = 4, and this implies that K3,3 is not planar. Any graph containing a nonplanar graph as a subgraph is nonplanar.

**What is meant by non-planar?**

Definition of nonplanar : not planar : not lying or able to be confined within a single plane : having a three-dimensional quality … there is no way of redrawing this circuit so that none of the elements cross. This, therefore, is an example of a nonplanar circuit.—

## How do you find the planarity of a graph?

To show that a given graph is planar we have to just draw it in a plane and if it can be drawn with the condition that no two edges are intersecting each other than we can say that the given graph is planar.

**What is a bipartite graph?**

Bipartite Graph – If the vertex-set of a graph G can be split into two disjoint sets, V 1 and V 2 , in such a way that each edge in the graph joins a vertex in V 1 to a vertex in V 2 , and there are no edges in G that connect two vertices in V 1 or two vertices in V 2 , then the graph G is called a bipartite graph.

**How to find if a graph is bipartite using BFS?**

Following is a simple algorithm to find out whether a given graph is Bipartite or not using Breadth First Search (BFS). 1. Assign RED color to the source vertex (putting into set U). 2. Color all the neighbors with BLUE color (putting into set V).

### How to check whether a given graph is 2-colorable or not?

One approach is to check whether the graph is 2-colorable or not using backtracking algorithm m coloring problem . Following is a simple algorithm to find out whether a given graph is Bipartite or not using Breadth First Search (BFS). 1. Assign RED color to the source vertex (putting into set U).