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[cpp] Update weighted graph

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+ totalWeight is now tracked for BFS & DFS traversals
+ Refactor graph search info structs
This commit is contained in:
Shaun Reed
2022-04-14 14:20:59 -04:00
parent 4b47630548
commit 34f12250ab
5 changed files with 106 additions and 93 deletions
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102
cpp/algorithms/graphs/weighted/lib-graph.cpp
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@@ -14,13 +14,13 @@
InfoBFS Graph::BFS(const Node& startNode) const
{
// Create local object to track the information gathered during traversal
InfoBFS searchInfo;
InfoBFS bfs;
// Create a queue to visit discovered nodes in FIFO order
std::queue<const Node *> visitQueue;
// Mark the startNode as in progress until we finish checking adjacent nodes
searchInfo[startNode.number].discovered = Gray;
bfs.nodeInfo[startNode.number].discovered = Gray;
// Visit the startNode
visitQueue.push(&startNode);
@@ -31,17 +31,17 @@ InfoBFS Graph::BFS(const Node& startNode) const
const 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 (searchInfo[adjacent.first].discovered == White) {
if (bfs.nodeInfo[adjacent.first].discovered == White) {
std::cout << "Found undiscovered adjacentNode: " << adjacent.first
<< "\n";
<< " with weight of " << adjacent.second << std::endl;
bfs.totalWeight += adjacent.second;
// Mark the adjacent node as in progress
searchInfo[adjacent.first].discovered = Gray;
searchInfo[adjacent.first].distance =
searchInfo[thisNode->number].distance + 1;
searchInfo[adjacent.first].predecessor =
bfs.nodeInfo[adjacent.first].discovered = Gray;
bfs.nodeInfo[adjacent.first].distance =
bfs.nodeInfo[thisNode->number].distance + 1;
bfs.nodeInfo[adjacent.first].predecessor =
&GetNode(thisNode->number);
// Add the discovered node the the visitQueue
@@ -49,11 +49,11 @@ InfoBFS Graph::BFS(const Node& startNode) const
}
}
// We are finished with this node and the adjacent nodes; Mark it discovered
searchInfo[thisNode->number].discovered = Black;
bfs.nodeInfo[thisNode->number].discovered = Black;
}
// Return the information gathered from this search, JIC caller needs it
return searchInfo;
return bfs;
}
std::deque<Node> Graph::PathBFS(const Node &start, const Node &finish) const
@@ -62,8 +62,8 @@ std::deque<Node> Graph::PathBFS(const Node &start, const Node &finish) const
// + If the caller modifies these, it will not impact the graph's data
std::deque<Node> path;
InfoBFS searchInfo = BFS(start);
const Node * next = searchInfo[finish.number].predecessor;
InfoBFS bfs = BFS(start);
const Node * next = bfs.nodeInfo[finish.number].predecessor;
bool isValid = false;
do {
// If we have reached the start node, we have found a valid path
@@ -74,7 +74,7 @@ std::deque<Node> Graph::PathBFS(const Node &start, const Node &finish) const
path.emplace_front(*next);
// Move to the next node
next = searchInfo[next->number].predecessor;
next = bfs.nodeInfo[next->number].predecessor;
} while (next != nullptr);
// Use emplace_back to call Node copy constructor
path.emplace_back(finish);
@@ -89,85 +89,83 @@ std::deque<Node> Graph::PathBFS(const Node &start, const Node &finish) const
InfoDFS Graph::DFS() const
{
// Track the nodes we have discovered
InfoDFS searchInfo;
InfoDFS dfs;
int time = 0;
// Visit each node in the graph
for (const auto& node : nodes_) {
for (const auto & node : nodes_) {
std::cout << "Visiting node " << node.number << std::endl;
// If the node is undiscovered, visit it
if (searchInfo[node.number].discovered == White) {
if (dfs.nodeInfo[node.number].discovered == White) {
std::cout << "Found undiscovered node: " << node.number << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(time, node, searchInfo);
DFSVisit(time, node, dfs);
}
}
return searchInfo;
return dfs;
}
InfoDFS Graph::DFS(const Node &startNode) const
{
// Track the nodes we have discovered
InfoDFS searchInfo;
InfoDFS dfs;
int time = 0;
auto startIter = std::find(nodes_.begin(), nodes_.end(),
Node(startNode.number, {})
);
auto startIter =
std::find(nodes_.begin(), nodes_.end(), Node(startNode.number, { }));
// beginning at startNode, visit each node in the graph until we reach the end
while (startIter != nodes_.end()) {
std::cout << "Visiting node " << startIter->number << std::endl;
// If the startIter is undiscovered, visit it
if (searchInfo[startIter->number].discovered == White) {
std::cout << "Found undiscovered node: " << startIter->number << std::endl;
if (dfs.nodeInfo[startIter->number].discovered == White) {
std::cout << "Found undiscovered node: " << startIter->number
<< std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(time, *startIter, searchInfo);
DFSVisit(time, *startIter, dfs);
}
startIter++;
}
// Once we reach the last node, check the beginning for unchecked nodes
startIter = nodes_.begin();
// Once we reach the initial startNode, we have checked all nodes
while (*startIter != startNode) {
std::cout << "Visiting node " << startIter->number << std::endl;
// If the startIter is undiscovered, visit it
if (searchInfo[startIter->number].discovered == White) {
if (dfs.nodeInfo[startIter->number].discovered == White) {
std::cout << "Found undiscovered node: " << startIter->number << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(time, *startIter, searchInfo);
DFSVisit(time, *startIter, dfs);
}
startIter++;
}
return searchInfo;
return dfs;
}
void Graph::DFSVisit(int &time, const Node& startNode, InfoDFS &searchInfo) const
void Graph::DFSVisit(int &time, const Node& startNode, InfoDFS &dfs) const
{
searchInfo[startNode.number].discovered = Gray;
dfs.nodeInfo[startNode.number].discovered = Gray;
time++;
searchInfo[startNode.number].discoveryFinish.first = time;
dfs.nodeInfo[startNode.number].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.first, {}));
for (const auto & adjacent : startNode.adjacent) {
const auto node = GetNode(adjacent.first);
// If the adjacentNode is undiscovered, visit it
// + Offset by 1 to account for 0 index of discovered vector
if (searchInfo[iter->number].discovered == White) {
std::cout << "Found undiscovered adjacentNode: "
<< GetNode(adjacent.first).number << std::endl;
if (dfs.nodeInfo[node.number].discovered == White) {
std::cout << "Found undiscovered adjacentNode: " << adjacent.first
<< " with weight of " << adjacent.second << std::endl;
// Visiting the undiscovered node will check it's adjacent nodes
DFSVisit(time, *iter, searchInfo);
dfs.totalWeight += adjacent.second;
DFSVisit(time, node, dfs);
}
}
searchInfo[startNode.number].discovered = Black;
dfs.nodeInfo[startNode.number].discovered = Black;
time++;
searchInfo[startNode.number].discoveryFinish.second = time;
dfs.nodeInfo[startNode.number].discoveryFinish.second = time;
}
std::vector<Node> Graph::TopologicalSort(const Node &startNode) const
@@ -177,8 +175,8 @@ std::vector<Node> Graph::TopologicalSort(const Node &startNode) const
std::vector<Node> order(nodes_);
auto comp = [&topological](const Node &a, const Node &b) {
return (topological[a.number].discoveryFinish.second <
topological[b.number].discoveryFinish.second);
return (topological.nodeInfo[a.number].discoveryFinish.second <
topological.nodeInfo[b.number].discoveryFinish.second);
};
std::sort(order.begin(), order.end(), comp);
@@ -190,26 +188,26 @@ std::vector<Node> Graph::TopologicalSort(const Node &startNode) const
InfoMST Graph::KruskalMST() const
{
InfoMST searchInfo(nodes_);
InfoMST mst(nodes_);
// The ctor for InfoMST initializes all edges within the graph into a multimap
// + Key for multimap is edge weight, so they're already sorted in ascending
// For each edge in the graph, check if they are part of the same tree
// + Since we do not want to create a cycle in the MST forest -
// + we don't connect nodes that are part of the same tree
for (const auto &edge : searchInfo.edges) {
for (const auto &edge : mst.edges) {
// Two integers representing the node.number for the connected nodes
const int u = edge.second.first;
const int v = edge.second.second;
// Check if the nodes are of the same tree
if (searchInfo.FindSet(u) != searchInfo.FindSet(v)) {
if (mst.FindSet(u) != mst.FindSet(v)) {
// If they are not, add the edge to our MST
searchInfo.edgesMST.emplace(edge);
searchInfo.weightMST += edge.first;
mst.edgesMST.emplace(edge);
mst.totalWeight += edge.first;
// Update the forest to reflect this change
searchInfo.Union(u, v);
mst.Union(u, v);
}
}
return searchInfo;
return mst;
}