void topSortDFS(DirectedGraphNode* node, unordered_map<DirectedGraphNode*, vector<DirectedGraphNode*>>& parents, unordered_set<DirectedGraphNode*>& visited, vector<DirectedGraphNode*>& result)
{
if (visited.insert(node).second)
{
for (DirectedGraphNode* parent : parents[node])
{
topSortDFS(parent, parents, visited, result);
}
result.push_back(node);
}
}
void topSortDFS(
DirectedGraphNode *node,
unordered_map<DirectedGraphNode *, vector<DirectedGraphNode *>> &ancestors,
unordered_set<DirectedGraphNode *> &scheduled,
vector<DirectedGraphNode *> &output) {
if (scheduled.insert(node).second) {
for (auto& ancestor: ancestors[node]) {
topSortDFS(ancestor, ancestors, scheduled, output);
}
output.emplace_back(node);
}
}
vector<DirectedGraphNode*> topSort(vector<DirectedGraphNode*> graph)
{
vector<DirectedGraphNode*>result;
unordered_set<DirectedGraphNode*> visited;
unordered_map<DirectedGraphNode*, vector<DirectedGraphNode*>> parents;
for (DirectedGraphNode* node : graph)
{
findParents(node, visited, parents);
}
visited.clear();
for (DirectedGraphNode* node : graph)
{
topSortDFS(node, parents, visited, result);
}
return result;
}
// @param graph: A list of Directed graph node
// @return: Any topological order for the given graph.
//
vector<DirectedGraphNode *> topSort(vector<DirectedGraphNode*> graph) {
vector<DirectedGraphNode *> output;
// Find ancestors of each node by DFS
unordered_set<DirectedGraphNode *> nodes;
unordered_map<DirectedGraphNode *, vector<DirectedGraphNode *>> ancestors;
for (auto& node :graph) {
findDependencyDFS(node, nodes, ancestors);
}
// Output topological order by DFS
unordered_set<DirectedGraphNode *> scheduled;
for (auto& node : graph) {
topSortDFS(node, ancestors, scheduled, output);
}
return output;
}
