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

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/*##############################################################################
## Author: Shaun Reed ##
## Legal: All Content (c) 2021 Shaun Reed, all rights reserved ##
## About: Driver program to test object graph implementation ##
## ##
## Contact: shaunrd0@gmail.com | URL: www.shaunreed.com | GitHub: shaunrd0 ##
################################################################################
*/
#include "lib-graph.hpp"
void Graph::BFS(const Node& startNode) const
{
// Track the nodes we have discovered
// TODO: Do this at the end to maintain the state instead of at beginning?
for (const auto &node : nodes_) node.color = White;
// Create a queue to visit discovered nodes in FIFO order
std::queue<Node> visitQueue;
// Mark the startNode as in progress until we finish checking adjacent nodes
startNode.color = Gray;
// Visit the startNode
visitQueue.push(startNode);
// Continue to visit nodes until there are none left in the graph
while (!visitQueue.empty()) {
// Remove thisNode from the visitQueue, storing its vertex locally
Node thisNode = visitQueue.front();
visitQueue.pop();
std::cout << "Visiting node " << thisNode.number << std::endl;
// Check if we have already discovered all the adjacentNodes to thisNode
for (const auto &adjacent : thisNode.adjacent) {
if (nodes_[adjacent - 1].color == White) {
std::cout << "Found undiscovered adjacentNode: " << adjacent << "\n";
// Mark the adjacent node as in progress
nodes_[adjacent - 1].color = Gray;
// Add the discovered node the the visitQueue
visitQueue.push(nodes_[adjacent - 1]);
}
}
// We are finished with this node and the adjacent nodes; Mark it discovered
thisNode.color = Black;
}
}
void Graph::DFS() const
{
// Track the nodes we have discovered
for (const auto &node : nodes_) node.color = White;
int time = 0;
// Visit each node in the graph
for (const auto& node : nodes_) {
std::cout << "Visiting node " << node.number << std::endl;
// If the node is undiscovered, visit it
if (node.color == White) {
std::cout << "Found undiscovered node: " << node.number << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(time, node);
}
}
}
void Graph::DFSVisit(int &time, const Node& startNode) const
{
startNode.color = Gray;
time++;
startNode.discoveryFinish.first = time;
// Check the adjacent nodes of the startNode
for (const auto &adjacent : startNode.adjacent) {
auto iter = std::find(nodes_.begin(), nodes_.end(),
Node(adjacent, {}));
// If the adjacentNode is undiscovered, visit it
// + Offset by 1 to account for 0 index of discovered vector
if (iter->color == White) {
std::cout << "Found undiscovered adjacentNode: "
<< nodes_[adjacent - 1].number << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(time, *iter);
}
}
startNode.color = Black;
time++;
startNode.discoveryFinish.second = time;
}
std::vector<Node> Graph::TopologicalSort() const
{
DFS();
std::vector<Node> topological(nodes_);
std::sort(topological.begin(), topological.end(), Node::FinishedSort);
// The topologicalOrder is read right-to-left in the final result
// + Output is handled in main as FILO, similar to a stack
return topological;
}