MoonTools.Graph/Graph/DirectedGraph.cs

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using System;
using System.Collections.Generic;
using System.Linq;
namespace MoonTools.Core.Graph
{
public enum SearchSymbol
{
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Start,
Finish
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}
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public class DirectedGraph<TNode, TEdgeData> : IGraph<TNode, TEdgeData> where TNode : IEquatable<TNode>
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{
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protected HashSet<TNode> nodes = new HashSet<TNode>();
protected HashSet<(TNode, TNode)> edges = new HashSet<(TNode, TNode)>();
protected Dictionary<(TNode, TNode), TEdgeData> edgesToEdgeData = new Dictionary<(TNode, TNode), TEdgeData>();
protected Dictionary<TNode, HashSet<TNode>> neighbors = new Dictionary<TNode, HashSet<TNode>>();
private class SimpleCycleComparer : IEqualityComparer<IEnumerable<TNode>>
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{
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public bool Equals(IEnumerable<TNode> x, IEnumerable<TNode> y)
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{
return x.SequenceEqual(y);
}
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public int GetHashCode(IEnumerable<TNode> obj)
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{
return obj.Aggregate(0, (current, next) => current.GetHashCode() ^ next.GetHashCode());
}
}
public IEnumerable<TNode> Nodes => nodes;
public IEnumerable<(TNode, TNode)> Edges => edges;
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public int Order => nodes.Count;
public int Size => edges.Count;
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public void AddNode(TNode node)
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{
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if (!Exists(node))
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{
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nodes.Add(node);
neighbors.Add(node, new HashSet<TNode>());
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}
}
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public void AddNodes(params TNode[] nodes)
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{
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foreach (var node in nodes)
{
AddNode(node);
}
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}
public bool Exists(TNode node)
{
return nodes.Contains(node);
}
public bool Exists(TNode v, TNode u)
{
return edges.Contains((v, u));
}
private void CheckNodes(params TNode[] givenNodes)
{
foreach (var node in givenNodes)
{
if (!Exists(node))
{
throw new ArgumentException($"Vertex {node} does not exist in the graph");
}
}
}
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public int Degree(TNode node)
{
CheckNodes(node);
return neighbors[node].Count;
}
readonly List<(TNode, TNode)> edgesToRemove = new List<(TNode, TNode)>();
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public void RemoveNode(TNode node)
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{
CheckNodes(node);
edgesToRemove.Clear();
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foreach (var entry in neighbors)
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{
if (entry.Value.Contains(node))
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{
edgesToRemove.Add((entry.Key, node));
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}
}
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foreach (var edge in edgesToRemove)
{
RemoveEdge(edge.Item1, edge.Item2);
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}
nodes.Remove(node);
neighbors.Remove(node);
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}
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public virtual void AddEdge(TNode v, TNode u, TEdgeData edgeData)
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{
CheckNodes(v, u);
neighbors[v].Add(u);
edges.Add((v, u));
edgesToEdgeData.Add((v, u), edgeData);
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}
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public virtual void AddEdges(params (TNode, TNode, TEdgeData)[] edges)
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{
foreach (var edge in edges)
{
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AddEdge(edge.Item1, edge.Item2, edge.Item3);
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}
}
private void CheckEdge(TNode v, TNode u)
{
CheckNodes(v, u);
if (!Exists(v, u)) { throw new ArgumentException($"Edge between vertex {v} and vertex {u} does not exist in the graph"); }
}
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public virtual void RemoveEdge(TNode v, TNode u)
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{
CheckEdge(v, u);
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neighbors[v].Remove(u);
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edges.Remove((v, u));
edgesToEdgeData.Remove((v, u));
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}
public TEdgeData EdgeData(TNode v, TNode u)
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{
CheckEdge(v, u);
return edgesToEdgeData[(v, u)];
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}
public IEnumerable<TNode> Neighbors(TNode node)
{
CheckNodes(node);
return neighbors[node];
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}
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readonly Stack<TNode> dfsStack = new Stack<TNode>();
readonly HashSet<TNode> dfsDiscovered = new HashSet<TNode>();
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public IEnumerable<TNode> PreorderNodeDFS()
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{
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dfsStack.Clear();
dfsDiscovered.Clear();
foreach (var node in Nodes)
{
if (!dfsDiscovered.Contains(node))
{
dfsStack.Push(node);
while (dfsStack.Count > 0)
{
var current = dfsStack.Pop();
if (!dfsDiscovered.Contains(current))
{
dfsDiscovered.Add(current);
yield return current;
foreach (var neighbor in Neighbors(current))
{
dfsStack.Push(neighbor);
}
}
}
}
}
}
// public IEnumerable<TNode> PostorderNodeDFS()
// {
// dfsStack.Clear();
// dfsDiscovered.Clear();
// foreach (var node in Nodes)
// {
// if (!dfsDiscovered.Contains(node))
// {
// dfsStack.Push(node);
// while (dfsStack.Count > 0)
// {
// var current = dfsStack.Pop();
// if (!dfsDiscovered.Contains(current))
// {
// dfsDiscovered.Add(current);
// foreach (var neighbor in Neighbors(current))
// {
// dfsStack.Push(neighbor);
// }
// yield return current;
// }
// }
// }
// }
// }
List<TNode> postorderOutput = new List<TNode>();
public IEnumerable<TNode> PostorderNodeDFS()
{
dfsDiscovered.Clear();
postorderOutput.Clear();
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void dfsHelper(TNode v) // refactor this to remove closure
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{
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dfsDiscovered.Add(v);
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foreach (var neighbor in Neighbors(v))
{
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if (!dfsDiscovered.Contains(neighbor))
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{
dfsHelper(neighbor);
}
}
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postorderOutput.Add(v);
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}
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foreach (var node in Nodes)
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{
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if (!dfsDiscovered.Contains(node))
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{
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dfsHelper(node);
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}
}
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return postorderOutput;
}
readonly Queue<TNode> bfsQueue = new Queue<TNode>();
readonly HashSet<TNode> bfsDiscovered = new HashSet<TNode>();
public IEnumerable<TNode> NodeBFS()
{
bfsQueue.Clear();
bfsDiscovered.Clear();
foreach (var node in Nodes)
{
if (!bfsDiscovered.Contains(node))
{
bfsQueue.Enqueue(node);
while (bfsQueue.Count > 0)
{
var current = bfsQueue.Dequeue();
foreach (var neighbor in Neighbors(current))
{
if (!bfsDiscovered.Contains(neighbor))
{
bfsDiscovered.Add(neighbor);
bfsQueue.Enqueue(neighbor);
yield return neighbor;
}
}
}
}
}
}
// hoo boy this is bad for the GC
public IEnumerable<TNode> LexicographicBFS()
{
var sets = new List<List<TNode>>();
sets.Add(Nodes.ToList());
while (sets.Count > 0)
{
var firstSet = sets[0];
var node = firstSet[0];
firstSet.RemoveAt(0);
if (firstSet.Count == 0) { sets.RemoveAt(0); }
yield return node;
var replaced = new List<List<TNode>>();
foreach (var neighbor in Neighbors(node))
{
if (sets.Any(set => set.Contains(neighbor)))
{
var s = sets.Find(set => set.Contains(neighbor));
var sIndex = sets.IndexOf(s);
List<TNode> t;
if (replaced.Contains(s))
{
t = sets[sIndex - 1];
}
else
{
t = new List<TNode>();
sets.Insert(sIndex, t);
replaced.Add(s);
}
s.Remove(neighbor);
t.Add(neighbor);
if (s.Count == 0) { sets.Remove(s); }
}
}
}
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}
public bool Cyclic()
{
return StronglyConnectedComponents().Any((scc) => scc.Count() > 1);
}
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public IEnumerable<TNode> TopologicalSort()
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{
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return PostorderNodeDFS().Reverse();
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}
readonly Dictionary<TNode, uint> preorder = new Dictionary<TNode, uint>();
readonly Dictionary<TNode, uint> lowlink = new Dictionary<TNode, uint>();
readonly Dictionary<TNode, bool> sccFound = new Dictionary<TNode, bool>();
readonly Stack<TNode> sccQueue = new Stack<TNode>();
readonly List<List<TNode>> sccResult = new List<List<TNode>>();
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public IEnumerable<IEnumerable<TNode>> StronglyConnectedComponents()
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{
preorder.Clear();
lowlink.Clear();
sccFound.Clear();
sccQueue.Clear();
sccResult.Clear();
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uint preorderCounter = 0;
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foreach (var source in Nodes)
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{
if (!sccFound.ContainsKey(source))
{
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var queue = new Stack<TNode>();
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queue.Push(source);
while (queue.Count > 0)
{
var v = queue.Peek();
if (!preorder.ContainsKey(v))
{
preorderCounter++;
preorder[v] = preorderCounter;
}
var done = true;
var vNeighbors = Neighbors(v);
foreach (var w in vNeighbors)
{
if (!preorder.ContainsKey(w))
{
queue.Push(w);
done = false;
break;
}
}
if (done)
{
lowlink[v] = preorder[v];
foreach (var w in vNeighbors)
{
if (!sccFound.ContainsKey(w))
{
if (preorder[w] > preorder[v])
{
lowlink[v] = Math.Min(lowlink[v], lowlink[w]);
}
else
{
lowlink[v] = Math.Min(lowlink[v], preorder[w]);
}
}
}
queue.Pop();
if (lowlink[v] == preorder[v])
{
sccFound[v] = true;
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var scc = new List<TNode>
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{
v
};
while (sccQueue.Count > 0 && preorder[sccQueue.Peek()] > preorder[v])
{
var k = sccQueue.Pop();
sccFound[k] = true;
scc.Add(k);
}
sccResult.Add(scc);
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}
else
{
sccQueue.Push(v);
}
}
}
}
}
return sccResult;
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}
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public IEnumerable<IEnumerable<TNode>> SimpleCycles()
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{
void unblock(TNode thisnode, HashSet<TNode> blocked, Dictionary<TNode, HashSet<TNode>> B) //refactor to remove closure
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{
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var stack = new Stack<TNode>();
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stack.Push(thisnode);
while (stack.Count > 0)
{
var node = stack.Pop();
if (blocked.Contains(thisnode))
{
blocked.Remove(thisnode);
if (B.ContainsKey(node))
{
foreach (var n in B[node])
{
if (!stack.Contains(n))
{
stack.Push(n);
}
}
B[node].Clear();
}
}
}
}
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List<List<TNode>> result = new List<List<TNode>>();
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var subGraph = Clone();
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var sccs = new Stack<IEnumerable<TNode>>();
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foreach (var scc in StronglyConnectedComponents())
{
sccs.Push(scc);
}
while (sccs.Count > 0)
{
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var scc = new Stack<TNode>(sccs.Pop());
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var startNode = scc.Pop();
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var path = new Stack<TNode>();
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path.Push(startNode);
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var blocked = new HashSet<TNode>
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{
startNode
};
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var closed = new HashSet<TNode>();
var B = new Dictionary<TNode, HashSet<TNode>>();
var stack = new Stack<Tuple<TNode, Stack<TNode>>>();
stack.Push(Tuple.Create(startNode, new Stack<TNode>(subGraph.Neighbors(startNode))));
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while (stack.Count > 0)
{
var entry = stack.Peek();
var thisnode = entry.Item1;
var neighbors = entry.Item2;
if (neighbors.Count > 0)
{
var nextNode = neighbors.Pop();
if (nextNode.Equals(startNode))
{
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var resultPath = new List<TNode>();
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foreach (var v in path)
{
resultPath.Add(v);
}
result.Add(resultPath);
foreach (var v in path)
{
closed.Add(v);
}
}
else if (!blocked.Contains(nextNode))
{
path.Push(nextNode);
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stack.Push(Tuple.Create(nextNode, new Stack<TNode>(subGraph.Neighbors(nextNode))));
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closed.Remove(nextNode);
blocked.Add(nextNode);
continue;
}
}
if (neighbors.Count == 0)
{
if (closed.Contains(thisnode))
{
unblock(thisnode, blocked, B);
}
else
{
foreach (var neighbor in subGraph.Neighbors(thisnode))
{
if (!B.ContainsKey(neighbor))
{
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B[neighbor] = new HashSet<TNode>();
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}
B[neighbor].Add(thisnode);
}
}
stack.Pop();
path.Pop();
}
}
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subGraph.RemoveNode(startNode);
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var H = subGraph.SubGraph(scc.ToArray());
var HSccs = H.StronglyConnectedComponents();
foreach (var HScc in HSccs)
{
sccs.Push(HScc);
}
}
return result.Distinct(new SimpleCycleComparer());
}
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public DirectedGraph<TNode, TEdgeData> Clone()
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{
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var clone = new DirectedGraph<TNode, TEdgeData>();
clone.AddNodes(Nodes.ToArray());
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foreach (var v in Nodes)
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{
foreach (var n in Neighbors(v))
{
clone.AddEdge(v, n, EdgeData(v, n));
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}
}
return clone;
}
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public DirectedGraph<TNode, TEdgeData> SubGraph(params TNode[] subVertices)
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{
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var subGraph = new DirectedGraph<TNode, TEdgeData>();
subGraph.AddNodes(subVertices.ToArray());
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foreach (var n in Nodes)
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{
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if (Nodes.Contains(n))
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{
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var neighbors = Neighbors(n);
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foreach (var u in neighbors)
{
if (subVertices.Contains(u))
{
subGraph.AddEdge(n, u, EdgeData(n, u));
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}
}
}
}
return subGraph;
}
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public void Clear()
{
nodes.Clear();
neighbors.Clear();
edges.Clear();
edgesToEdgeData.Clear();
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}
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}
}