dfs exit action

DKey.Algorithms.Tests/Graph/DFSTests.cs

@@ -24,6 +24,25 @@ public void Iterative_GivenGraph_ReturnsExpectedTraversal()
 
         Assert.That(traversal, Is.EqualTo(new[] { 0, 1, 3, 4, 2 }));
     }
+
+    [Test]
+    public void IterativeWithExitExtiOn_GivenGraph_ReturnsExpectedTraversal()
+    {
+        var graph = new[]
+        {
+            new List<int> { 1, 2 },
+            new List<int> { 3, 4 },
+            new List<int>(),
+            new List<int>(),
+            new List<int>(),
+        };
+        var context = new DFSContext(graph, 0);
+        var traversal = new List<int>();
+
+        DFS.IterativeWithExitAction(context, null, c => traversal.Add(c.CurrentVertex));
+
+        Assert.That(traversal, Is.EqualTo(new[] { 3, 4, 1, 2, 0 }));
+    }
 
     [Test]
     public void Recursive_GivenGraph_ReturnsExpectedTraversal()

DKey.Algorithms.sln.DotSettings.user

@@ -1,7 +1,9 @@
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@@ -11,16 +13,7 @@
 
 
 
-	<s:String x:Key="/Default/Environment/UnitTesting/UnitTestSessionStore/Sessions/=da0784d7_002Dba34_002D413e_002D82f5_002Da990c8d84b73/@EntryIndexedValue">&lt;SessionState ContinuousTestingMode="0" IsActive="True" Name="Tests" xmlns="urn:schemas-jetbrains-com:jetbrains-ut-session"&gt;&#xD;
-  &lt;Not&gt;&#xD;
-    &lt;And&gt;&#xD;
-      &lt;Project Location="C:\Repos\github\DKey.Algorithms\Dkey.Algorithms.Tests" Presentation="&amp;lt;DKey.Algorithms.Tests&amp;gt;" /&gt;&#xD;
-      &lt;TestAncestor&gt;&#xD;
-        &lt;TestId&gt;NUnit3x::705969DA-A152-47DC-9BB6-D5060B8D81F0::net7.0::DKey.Algorithms.Tests.Search.GoldenSectionSearchTests.Test_InvalidRange&lt;/TestId&gt;&#xD;
-      &lt;/TestAncestor&gt;&#xD;
-    &lt;/And&gt;&#xD;
-  &lt;/Not&gt;&#xD;
-&lt;/SessionState&gt;</s:String>
+
 
 
 

DKey.Algorithms/DataStructures/Graph/DepthFirstSearch/DFS.cs

@@ -48,6 +48,61 @@ public static void Iterative<TContext>(TContext context, Action<TContext>? actio
             }
         }
     }
+
+    /// <summary>
+    /// Iterative depth-first search with some action on the current context.
+    /// Use this for big graphs to avoid stack overflow.
+    /// Can be more memory efficient if you push vertices 1 by 1 tracking how many children ha been pushed, but this is easier to understand.
+    /// </summary>
+    public static void IterativeWithExitAction<TContext>(TContext context, Action<TContext>? enterAction = default, Action<TContext>? exitAction = default, bool preallocate = false) where TContext : DFSContext
+    {
+        if(context.stopFlag)
+            return;
+        var stack = new Stack<int>(preallocate ? context.Graph.Length : 0);
+        stack.Push(context.CurrentVertex);
+        context.VertexInfo[context.CurrentVertex] = (-1, 0);
+
+        while (stack.Count > 0)
+        {
+            var currentVertex = stack.Peek();
+            context.CurrentVertex = currentVertex;
+
+            if (!context.Used.Contains(currentVertex))
+            {
+                //On entering the vertex.
+                enterAction?.Invoke(context);
+                context.Used.Add(currentVertex);
+                context.Parents.Push(currentVertex);
+
+                var wasPushed = false;
+                //Pushing children to the stack of vertices to visit.
+                for (int i = context.Graph[currentVertex].Count - 1; i >=0 ; i--)
+                {
+                    var nextAdjacent = context.Graph[currentVertex][i];
+                    if (!context.Used.Contains(nextAdjacent))
+                    {
+                        wasPushed = true;
+                        stack.Push(nextAdjacent);
+                        context.VertexInfo[nextAdjacent] = (currentVertex, context.TraverseDepth);
+                    }
+
+                }
+                if (wasPushed)
+                {
+                    continue;
+                }
+            }
+
+            //On exiting the vertex. If graph is not tree, we need to check current parent, to avoid removing vertex if it already was removed, but got visited through another branch.
+            if (context.Parents.Peek() == currentVertex)
+            {
+                context.Parents.Pop();
+                exitAction?.Invoke(context);
+            }
+            stack.Pop();
+        }
+    }
+
 
     /// <summary>
     /// Depth-first search with some action on current context

DKey.Algorithms/DataStructures/Graph/DepthFirstSearch/DFSTools.cs

@@ -0,0 +1,18 @@
+namespace DKey.Algorithms.DataStructures.Graph.DepthFirstSearch;
+
+public class DFSTools
+{
+    public List<int> Traverse(DFSContext context, bool reverse = false)
+    {
+        var result = new List<int>();
+        DFS.Iterative(context, x =>
+        {
+            result.Add(x.CurrentVertex);
+        });
+        if (reverse)
+        {
+            result.Reverse();
+        }
+        return result;
+    }
+}

DKey.CodeForces/Program.cs

@@ -1,11 +1,12 @@
 using DKey.Algorithms;
-using DKey.CodeForces.Contest2103;
+using DKey.CodeForces.Contest2117;
+using DKey.CodeForces.Sandbox;
 
 namespace DKey.CodeForces;
 
 public static class Program
 {
-    private static Solver _solver = new Solver2103D();
+    private static Solver _solver = new SandboxSolver();
     public static void Main()
     {
         _solver.Run();

DKey.CodeForces/Sandbox/SandboxSolver.cs

@@ -0,0 +1,43 @@
+using DKey.Algorithms;
+using DKey.Algorithms.DataStructures.Graph;
+using DKey.Algorithms.DataStructures.Graph.DepthFirstSearch;
+
+namespace DKey.CodeForces.Sandbox;
+
+public class SandboxSolver : Solver
+{
+    public SandboxSolver() : base( new []{typeof(int)})
+    {
+    }
+
+    public override void Solve(object[] objects)
+    {
+        var roots = new HashSet<int>();
+        var n = (int) objects[0];
+        var edges = new List<(int, int)>();
+        for (var i = 0; i < n; i++)
+        {
+            var parent = IOHelper.ReadInt();
+            if (parent == -1)
+            {
+                roots.Add(i);
+                continue;
+            }
+
+            edges.Add((parent - 1, i));
+        }
+
+        var graph = GraphBuilder.Directed(edges, n);
+
+        var maxTraverseDepth = 0;
+        foreach (var root in roots)
+        {
+            var context = new DFSContext(graph.G, root);
+            DFS.IterativeWithExitAction(context, null, c =>
+            {
+                maxTraverseDepth = Math.Max(maxTraverseDepth, c.TraverseDepth);
+            });
+        }
+        output.AddLine(maxTraverseDepth + 1);
+    }
+}

DKey.ContestTemplateBuilder/Config.cs

@@ -3,6 +3,6 @@
 public class Config
 {
     public static string repoPath = @"C:\Repos\GitHub\DKey.Algorithms\DKey.CodeForces";
-    public static string contestID = "2103";
+    public static string contestID = "2117";
     public static int problemCount = 8;
 }