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

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/*##############################################################################
## 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 <utility>
#include <vector>
#include <queue>
#include <unordered_set>
// Color represents the discovery status of any given node
// + White is undiscovered, Gray is in progress, Black is fully discovered
enum Color {White, Gray, Black};
/******************************************************************************/
// Node structure for representing a graph
struct Node {
public:
// Constructors
Node(const Node &rhs) = default;
Node & operator=(Node rhs) {
if (this == &rhs) return *this;
swap(*this, rhs);
return *this;
}
Node(int num, std::vector<int> adj) : number(num), adjacent(std::move(adj)) {}
friend void swap(Node &a, Node &b) {
std::swap(a.number, b.number);
std::swap(a.adjacent, b.adjacent);
std::swap(a.color, b.color);
std::swap(a.discoveryFinish, b.discoveryFinish);
}
// Don't allow anyone to change these values when using a const reference
int number;
std::vector<int> adjacent;
// Mutable members so we can update these values when using a const reference
// + Since they need to be modified during traversals
// Coloring of the nodes are used in both DFS and BFS
mutable Color color = White;
// Used in BFS to represent distance from start node
mutable int distance = 0;
// Used in BFS to represent the parent node that discovered this node
// + If we use this node as the starting point, this will remain a nullptr
mutable Node *predecessor = nullptr;
// Create a pair to track discovery / finish time when using DFS
// + Discovery time is the iteration the node is first discovered
// + Finish time is the iteration the node has been checked completely
// ++ A finished node has considered all adjacent nodes
mutable std::pair<int, int> discoveryFinish;
// Define a comparator for std::sort
// + This will help to sort nodes by finished time after traversal
static bool FinishedSort(const Node &node1, const Node &node2)
{ return node1.discoveryFinish.second < node2.discoveryFinish.second;}
// Define operator== for std::find
bool operator==(const Node &b) const { return this->number == b.number;}
};
/******************************************************************************/
// Graph class declaration
class Graph {
public:
// Constructor
explicit Graph(std::vector<Node> nodes) : nodes_(std::move(nodes)) {}
// Breadth First Search
void BFS(const Node& startNode) const;
std::deque<const Node *> PathBFS(const Node &start, const Node &finish) const;
// Depth First Search
void DFS() const;
void DFS(const Node &startNode) const;
void DFSVisit(int &time, const Node& startNode) const;
// Topological sort, using DFS
std::vector<Node> TopologicalSort(const Node &startNode) const;
// Returns a copy of a node with the number i within the graph
inline Node GetNodeCopy(int i) { return GetNode(i);}
// Return a constant iterator for reading node values
inline std::vector<Node>::const_iterator NodeBegin() { return nodes_.begin();}
private:
// A non-const accessor for direct access to a node with the number value i
inline Node & GetNode(int i)
{ return *std::find(nodes_.begin(), nodes_.end(), Node(i, {}));}
// For use with const member functions to access mutable values
inline const Node & GetNode(int i) const
{ return *std::find(nodes_.begin(), nodes_.end(), Node(i, {}));}
std::vector<Node> nodes_;
};
#endif // LIB_GRAPH_HPP