Add adjacency matrix implementation

Author: donald-pinckney

Graph/Graph.playground/Contents.swift renamed to Graph/Graph Adjacency List.playground/Contents.swift

@@ -0,0 +1,59 @@
+
+
+public struct GraphVertex<T> {
+  public var data: T
+  let uniqueID: Int
+}
+
+public struct Graph<T> {
+  
+  private var adjacencyMatrix: [[Int?]] = [] // row-major
+  
+  public init() { } // Silence default constructor
+  
+  public mutating func createVertex(data: T) -> GraphVertex<T> {
+    let vertex = GraphVertex(data: data, uniqueID: adjacencyMatrix.count)
+    
+    // Expand each existing row to the right one column
+    for i in 0..<adjacencyMatrix.count {
+      adjacencyMatrix[i].append(nil)
+    }
+    
+    // Add one new row at the bottom
+    let newRow = [Int?](count: adjacencyMatrix.count + 1, repeatedValue: nil)
+    adjacencyMatrix.append(newRow)
+    
+    return vertex
+  }
+  
+  // Creates a directed edge source -----> dest.  Represented by M[source][dest] = weight
+  public mutating func connect(sourceVertex: GraphVertex<T>, toDestinationVertex: GraphVertex<T>, withWeight weight: Int = 0) {
+    adjacencyMatrix[sourceVertex.uniqueID][toDestinationVertex.uniqueID] = weight
+  }
+  
+  // Creates an undirected edge by making 2 directed edges: some ----> other, and other ----> some
+  public mutating func connect(someVertex: GraphVertex<T>, withVertex: GraphVertex<T>, withWeight weight: Int = 0) {
+    adjacencyMatrix[someVertex.uniqueID][withVertex.uniqueID] = weight
+    adjacencyMatrix[withVertex.uniqueID][someVertex.uniqueID] = weight
+
+  }
+}
+
+
+
+
+var graph = Graph<Int>()
+let v1 = graph.createVertex(1)
+let v2 = graph.createVertex(2)
+let v3 = graph.createVertex(3)
+let v4 = graph.createVertex(4)
+
+// v1 ---> v2 ---> v3 ---> v4
+// ^                       |
+// |                       V
+// -----------<------------|
+
+graph.connect(v1, toDestinationVertex: v2)
+graph.connect(v2, toDestinationVertex: v3)
+graph.connect(v3, toDestinationVertex: v4)
+graph.connect(v4, toDestinationVertex: v1)

Graph/Graph.playground/contents.xcplayground renamed to Graph/Graph Adjacency List.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Graph/Graph.playground/timeline.xctimeline renamed to Graph/Graph Adjacency List.playground/timeline.xctimeline

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline
+   version = "3.0">
+   <TimelineItems>
+   </TimelineItems>
+</Timeline>