shaunrd0/klips
1
0
Fork 0
Code Issues Pull Requests 1 Projects Releases Wiki Activity

Update object graph implementation to track node discover and finish time

Browse Source 
+ Allows traversal and topological sort algorithms to show examples from MIT Algorithms more accurately
This commit is contained in:
Shaun Reed
2021-06-28 12:46:04 -04:00
parent 5d37db1ce2
commit 348586ec38
4 changed files with 58 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
cpp/algorithms/graphs/object/lib-graph.cpp
View File

@@ -52,6 +52,7 @@ 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_) {
@@ -60,69 +61,43 @@ void Graph::DFS() const
if (node.color == White) {
std::cout << "Found undiscovered node: " << node.number << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(node);
DFSVisit(time, node);
}
}
}
void Graph::DFSVisit(const Node& startNode) const
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 (nodes_[adjacent - 1].color == White) {
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(nodes_[adjacent - 1]);
DFSVisit(time, *iter);
}
}
startNode.color = Black;
time++;
startNode.discoveryFinish.second = time;
}
std::vector<Node> Graph::TopologicalSort() const
{
std::vector<Node> topologicalOrder;
DFS();
std::vector<Node> topological(nodes_);
// Track the nodes we have discovered
for (const auto &node : nodes_) node.color = White;
// 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
TopologicalVisit(node, topologicalOrder);
}
}
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 topologicalOrder;
}
void Graph::TopologicalVisit(const Node &startNode,
std::vector<Node> &order) const
{
// Mark the node as visited so we don't visit it twice
startNode.color = Gray;
// Check the adjacent nodes of the startNode
for (const auto& adjacent : startNode.adjacent) {
// If the adjacentNode is undiscovered, visit it
if (nodes_[adjacent - 1].color == White) {
std::cout << "Found undiscovered adjacentNode: " << adjacent << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
TopologicalVisit(nodes_[adjacent - 1], order);
}
}
startNode.color = Black;
// Add startNode to the topologicalOrder
order.push_back(startNode);
return topological;
}