Find indegree and outdegree of a directed graph in swift

Swift program for Find indegree and outdegree of a directed graph. Here problem description and other solutions.

import Foundation
/*
    Swift 4 Program for 
    Show degree of vertex in directed graph
*/
class AjlistNode
{
	// Vertices node key
	var id: Int;
	var next: AjlistNode? ;
	init(_ id: Int)
	{
		// Set value of node key
		self.id = id;
		self.next = nil;
	}
}
class Vertices
{
	var data: Int;
	var next: AjlistNode? ;
	var last: AjlistNode? ;
	init(_ data: Int)
	{
		self.data = data;
		self.next = nil;
		self.last = nil;
	}
}
class Graph
{
	// Number of Vertices
	var size: Int;
	var node: [Vertices? ];
	init(_ size: Int)
	{
		// Set value
		self.size = size;
		self.node = Array(repeating: nil, count: size);
		self.setData();
	}
	// Set initial node value
	func setData()
	{
		if (self.size <= 0)
		{
			print("\nEmpty Graph");
		}
		else
		{
			var index: Int = 0;
			while (index < self.size)
			{
				// Set initial node value
				self.node[index] = Vertices(index);
				index += 1;
			}
		}
	}
	//  Handling the request of adding new edge
	func addEdge(_ start: Int, _ last: Int)
	{
		if (start >= 0 && start < self.size && last >= 0 && last < self.size)
		{
			// Safe connection
			let edge: AjlistNode? = AjlistNode(last);
			if (self.node[start]!.next == nil)
			{
				self.node[start]!.next = edge;
			}
			else
			{
				// Add edge at the end
				self.node[start]!.last!.next = edge;
			}
			// Get last edge 
			self.node[start]!.last = edge;
		}
		else
		{
			// When invalid nodes
			print("\nHere Something Wrong");
		}
	}
	func printGraph()
	{
		if (self.size > 0)
		{
			var index: Int = 0;
			// Print graph ajlist Node value
			while (index < self.size)
			{
				print("\nAdjacency list of vertex ", index, terminator: " : ");
				var temp: AjlistNode? = self.node[index]!.next;
				while (temp  != nil)
				{
					// Display graph node 
					print(self.node[temp!.id]!.data, 
                          terminator: " ");
					// Visit to next edge
					temp = temp!.next;
				}
				index += 1;
			}
		}
	}
	// Find indegree and outdegree of 
	// each nodes of a given graph
	func findDegree(_ indegree: inout [Int], 
      _ outdegree: inout [Int])
	{
		var temp: AjlistNode? = nil;
		var length: Int = 0;
		var i: Int = 0;
		while (i < self.size)
		{
			temp = self.node[i]!.next;
			length = 0;
			while (temp  != nil)
			{
				// Update indegree
				indegree[temp!.id] += 1;
				temp = temp!.next;
				length += 1;
			}
			// Set outdegree value
			outdegree[i] = length;
			i += 1;
		}
	}
	func showDegree()
	{
		if (self.size  > 0)
		{
			var indegree: [Int] = Array(repeating: 0, count: self.size);
			var outdegree: [Int] = Array(repeating: 0, count: self.size);
	
			// Find degree
			self.findDegree(&indegree, &outdegree);
			print("\n");
			var i: Int = 0;
			// Display result
			while (i < self.size)
			{
				print("Node [" + String(i) + 
                      "] indegree [" + String(indegree[i]) + 
                      "] outdegree [" + String(outdegree[i]) + "]");
				i += 1;
			}
		}
		else
		{
			print("Empty Graph", terminator: "");
		}
	}
	static func main(_ args: [String])
	{
		// 6 implies the number of nodes in graph
		let g: Graph? = Graph(6);
		// Connected two node with Edges
		g!.addEdge(0, 1);
		g!.addEdge(0, 2);
		g!.addEdge(0, 5);
		g!.addEdge(2, 3);
		g!.addEdge(3, 1);
		g!.addEdge(4, 0);
		g!.addEdge(4, 1);
		g!.addEdge(5, 0);
		g!.addEdge(5, 2);
		g!.printGraph();
		// Test
		g!.showDegree();
	}
}
Graph.main([String]());

Output

Adjacency list of vertex  0 : 1 2 5
Adjacency list of vertex  1 :
Adjacency list of vertex  2 : 3
Adjacency list of vertex  3 : 1
Adjacency list of vertex  4 : 0 1
Adjacency list of vertex  5 : 0 2

Node [0] indegree [2] outdegree [3]
Node [1] indegree [3] outdegree [0]
Node [2] indegree [2] outdegree [1]
Node [3] indegree [1] outdegree [1]
Node [4] indegree [0] outdegree [2]
Node [5] indegree [1] outdegree [2]