Write initial structs for Graph

Author: donald-pinckney

Graph/Graph.playground/Contents.swift

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+public struct GraphEdge<T> {
+    let from: GraphVertex<T>
+    let to: GraphVertex<T>
+    let weight: Int
+}
+
+public struct GraphVertex<T> {
+    public var data: T
+    private var edges: [GraphEdge<T>] // This is a simple adjacency list, rather than matrix
+    
+    public mutating func connectTo(destinationVertex: GraphVertex<T>, withWeight weight: Int = 0) {
+        edges.append(GraphEdge(from: self, to: destinationVertex, weight: weight))
+    }
+    
+    public mutating func connectBetween(inout otherVertex: GraphVertex<T>, withWeight weight: Int = 0) {
+        edges.append(GraphEdge(from: self, to: otherVertex, weight: weight))
+        otherVertex.edges.append(GraphEdge(from: otherVertex, to: self, weight: weight))
+    }
+}
+
+

Graph/Graph.playground/contents.xcplayground

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+<?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

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+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline
+   version = "3.0">
+   <TimelineItems>
+   </TimelineItems>
+</Timeline>

Graph/README.markdown

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+# Graph
+
+YAY Graphs!
+TODO: Write stuff here.
+
+*Written by Donald Pinckney*