PYTHON - EDGE LIST CODE

JAVA PYTHON GO KOTLIN C# RUBY C++ Java Script

Example :

class Edge:
    def getStartVertex(self):
        return self.startVertex

    def setStartVertex(self, startVertex):
        self.startVertex = startVertex;

    def getEndVertex(self):
        return self.endVertex

    def setEndVertex(self, endVertex):
        self.endVertex = endVertex

    def getValue(self):
        return self.value

    def setValue(self, value):
        self.value = value

def insertVertex(vertices, vertex):
    vertices.append(vertex)

def insertEdge(edgeList, vertex1, vertex2, edgeVal):
	edge = Edge()
	edge.setStartVertex(vertex1)
	edge.setEndVertex(vertex2)
	edge.setValue(edgeVal)
	edgeList.append(edge)

def printEdgeList(edgeList):
	for edge in edgeList:
		print("The Edge between", edge.getStartVertex(), "and", edge.getEndVertex(), "is", edge.getValue())
		

vertices = []

# Adding vertices one by one

insertVertex(vertices, "a")
insertVertex(vertices, "b")
insertVertex(vertices, "c")
insertVertex(vertices, "d")
insertVertex(vertices, "e")

edgeList = []

# Adding edges with values.

insertEdge(edgeList, "a", "b", "13A")
insertEdge(edgeList, "b", "a", "45C")
insertEdge(edgeList, "a", "d", "20F")
insertEdge(edgeList, "d", "e", "23E")
insertEdge(edgeList, "e", "b", "12B")
insertEdge(edgeList, "e", "c", "30F")
insertEdge(edgeList, "c", "d", "42V")
insertEdge(edgeList, "a", "c", "18C")

printEdgeList(edgeList)

Output :

The Edge between a and b is 13A
The Edge between b and a is 45C
The Edge between a and d is 20F
The Edge between d and e is 23E
The Edge between e and b is 12B
The Edge between e and c is 30F
The Edge between c and d is 42V
The Edge between a and c is 18C

Code explanation for Edge List Data Structure

In the Edge List Data Structure, we are trying to create a Linked List of Edges.

Where each Edge will contain the start vertex, end vertex and value of the Edge.

Say for Example, the first element of the Edge Linked List i.e. Bus number 13A, travels from city/Vertex a to city/Vertex b.

So, we will be having two pointers in the first element of Edge Linked List,

And thus, we have constructed an Edge class that contains, start vertex, end vertex and value of the Edge.

class Edge:
	def getStartVertex(self):
		return self.startVertex

	def setStartVertex(self, startVertex):
		self.startVertex = startVertex;

	def getEndVertex(self):
		return self.endVertex

	def setEndVertex(self, endVertex):
		self.endVertex = endVertex

	def getValue(self):
		return self.value

	def setValue(self, value):
		self.value = value

We have 2 methods in the Code :

def insertVertex(vertices, vertex)

def insertEdge(edgeList, vertex1, vertex2, edgeVal)

The first method is quite easy to understand.

Explanation of 'def insertVertex(vertices, vertex)' method :

def insertVertex(vertices, vertex):
	vertices.append(vertex)

Let us take the vertex a to understand the above method.

So, we have created a Array that would contain all the vertices :

vertices = []

Then we have taken the vertex a and passed it to the def insertVertex(...) method.

insertVertex(vertices, "a")

And if we see the void insertVertex(...) method, we would see it accepts two parameters,

vertices

and

vertex.

It is quite self explanatory, vertices contains the actual Array that contains the vertices and vertex contains the vertex a.

And we just have one statement in the def insertVertex(...) method.

vertices.append(vertex)

That takes each vertex a and adds to the Linked List.

After adding all the vertices to the LinkedList, we get the below LinkedList.

Then comes the second method, that adds the edges to the Linked List(with values). Justifying the name Edge List Data Structure.

Explanation of 'def insertEdge(edgeList, vertex1, vertex2, edgeVal)' method :

def insertEdge(edgeList, vertex1, vertex2, edgeVal):
	edge = Edge()
	edge.setStartVertex(vertex1)
	edge.setEndVertex(vertex2)
	edge.setValue(edgeVal)
	edgeList.append(edge)

We will take a small chunk to explain the above method.

Where the bus/edge 13A is traveling from city a to city b.

Now, we have created a Linked List that would store all the edges in that Linked List.

edgeList = []

Next, we will pass the edgeList, the start vertex(i.e. a), end vertex(i.e. b) and the value(i.e. 13A) to the def insertEdge(...) method.

insertEdge(edgeList, "a", "b", "13A")

Now, let us come to the contents of def insertEdge(...) method.

In the first line, we have created the Edge object,

edge = Edge()

Then, initialised the attributes of the Edge object with the actual values,

edge.setStartVertex(vertex1)
edge.setEndVertex(vertex2)
edge.setValue(edgeVal)

And the Edge object looks somewhat like this,

And add the above edge object to the Linked List,

edgeList.append(edge)

After adding all the edges to the Linked List, we get the below Linked List.

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