# Adjacency list representation of undirected graph in swift

Swift program for Adjacency list representation of undirected graph. Here problem description and explanation.

import Foundation
/*
Swift 4 Program for
Undirected graph representation by using adjacency list
*/
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)
{
self.node[index] = Vertices(index);
index += 1;
}
}
}
// Connect two nodes
func connect(_ start: Int, _ last: Int)
{
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;
}
//  Handling the request of adding new edge
func addEdge(_ start: Int, _ last: Int)
{
if (start >= 0 && start < self.size &&
last >= 0 && last < self.size)
{
self.connect(start, last);
if (start == last)
{
// When self loop
return;
}
self.connect(last, start);
}
else
{
// When invalid nodes
print("\nHere Something Wrong");
}
}
func printGraph()
{
if (self.size > 0)
{
do {
var index: Int = 0;
// Print graph ajlist Node value
while (index < self.size)
{
print("\nAdjacency list of vertex " + String(index),
terminator: " :");
var temp: AjlistNode? = self.node[index]!.next;
while (temp  != nil)
{
// Display graph node
print("  " + String(self.node[temp!.id]!.data),
terminator: "");
// Visit to next edge
temp = temp!.next;
}
index += 1;
}
}
}
}
static func main(_ args: [String])
{
// 5 implies the number of nodes in graph
let g: Graph? = Graph(5);
// Connect node with an edge
// print graph element
g!.printGraph();
}
}
Graph.main([String]());

Output

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

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