Add example of object graph traversal algorithms

+ Using pseudocode examples from MIT Intro to Algorithms

cpp/algorithms/graphs/object/lib-graph.hpp

@@ -0,0 +1,58 @@
+/*##############################################################################
+## Author: Shaun Reed                                                         ##
+## Legal: All Content (c) 2021 Shaun Reed, all rights reserved                ##
+## About: An example of an object graph implementation                        ##
+##        Algorithms in this example are found in MIT Intro to Algorithms     ##
+##                                                                            ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0   ##
+################################################################################
+*/
+#ifndef LIB_GRAPH_HPP
+#define LIB_GRAPH_HPP
+
+#include <iostream>
+#include <algorithm>
+#include <map>
+#include <set>
+#include <utility>
+#include <vector>
+#include <queue>
+
+// A vertex can also be referred to as a node
+// + ... Unless you are a mathematician ^.^
+struct Vertex {
+  // This vertex's number
+  int number;
+  // A set of all vertices adjacent to this vertex
+  std::set<int> adjacent;
+};
+
+enum Color {White, Gray, Black};
+
+struct Node {
+public:
+  Node(int num, std::set<int> adj) : number(num), adjacent(std::move(adj)) {}
+  int number;
+  std::set<int> adjacent;
+  // Mutable so we can update the color of the nodes during traversal
+  mutable Color color = White;
+  std::vector<int> predecessors;
+
+//  bool operator<(const Node &node1) const { return number < node1.number;}
+  inline void setColor(Color newColor) const { color = newColor;}
+};
+
+class Graph {
+public:
+  explicit Graph(std::vector<Node> nodes) : nodes_(std::move(nodes)) {}
+  std::vector<Node> nodes_;
+
+  void BFS(const Node& startNode) const;
+  void DFS() const;
+  void DFSVisit(const Node& startNode) const;
+  std::vector<Node> TopologicalSort() const;
+  void TopologicalVisit(const Node &startNode, std::vector<Node> &order) const;
+
+};
+
+#endif // LIB_GRAPH_HPP