Merge pull request #24 from MartinZikmund/feature/aoc2024-day23

AoC 2024 Day 23 Solutions

Author: MartinZikmund

src/AdventOfCode.Puzzles/2024/23/Part1/Part1.cs

@@ -0,0 +1,59 @@
+namespace AdventOfCode.Puzzles._2024._23.Part1;
+
+public partial class Part1 : IPuzzleSolution
+{
+    private Dictionary<string, HashSet<string>> _graph = new();
+
+    private HashSet<string> _vertices = new();
+
+    public async Task<string> SolveAsync(StreamReader inputReader)
+    {
+        var edges = await inputReader.ReadAllLinesAsync();
+
+        foreach (var edge in edges)
+        {
+            var neighbors = edge.Split("-");
+            foreach (var neighbor in neighbors)
+            {
+                if (!_graph.ContainsKey(neighbor))
+                {
+                    _graph[neighbor] = new HashSet<string>();
+                }
+
+                if (!_vertices.Contains(neighbor))
+                {
+                    _vertices.Add(neighbor);
+                }
+            }
+
+            _graph[neighbors[0]].Add(neighbors[1]);
+            _graph[neighbors[1]].Add(neighbors[0]);
+        }
+
+        var triangles = GetTrianglesWithT();
+
+        return triangles.Count.ToString();
+    }
+
+    private HashSet<string> GetTrianglesWithT()
+    {
+        var results = new HashSet<string>();
+        foreach (var vertex in _vertices.Where(v => v.StartsWith("t")))
+        {
+            foreach (var secondVertex in _vertices)
+            {
+                foreach (var thirdVertex in _vertices)
+                {
+                    if (_graph[vertex].Contains(secondVertex) &&
+                        _graph[secondVertex].Contains(thirdVertex) &&
+                        _graph[thirdVertex].Contains(vertex))
+                    {
+                        results.Add(string.Join(",", new[] { vertex, secondVertex, thirdVertex }.OrderBy(v => v)));
+                    }
+                }
+            }
+        }
+
+        return results;
+    }
+}

src/AdventOfCode.Puzzles/2024/23/Part2/Part2.cs

@@ -0,0 +1,92 @@
+namespace AdventOfCode.Puzzles._2024._23.Part2;
+
+public partial class Part2 : IPuzzleSolution
+{
+    private Dictionary<string, HashSet<string>> _graph = new();
+
+    private HashSet<string> _vertices = new();
+
+    public async Task<string> SolveAsync(StreamReader inputReader)
+    {
+        var edges = await inputReader.ReadAllLinesAsync();
+
+        foreach (var edge in edges)
+        {
+            var neighbors = edge.Split("-");
+            foreach (var neighbor in neighbors)
+            {
+                if (!_graph.ContainsKey(neighbor))
+                {
+                    _graph[neighbor] = new HashSet<string>();
+                }
+
+                if (!_vertices.Contains(neighbor))
+                {
+                    _vertices.Add(neighbor);
+                }
+            }
+
+            _graph[neighbors[0]].Add(neighbors[1]);
+            _graph[neighbors[1]].Add(neighbors[0]);
+        }
+
+        var triangles = GetTriangles();
+        var largestSet = FindLargestSet(triangles);
+        return largestSet;
+    }
+
+    private string FindLargestSet(HashSet<string> triangles)
+    {
+        var sortedVertices = _vertices.OrderBy(v => v).ToArray();
+
+        var currentSets = triangles;
+
+        var newSets = currentSets;
+        do
+        {
+            currentSets = newSets;
+            newSets = new HashSet<string>();
+
+            foreach (var currentSet in currentSets)
+            {
+                var verticesInSet = currentSet.Split(",");
+                foreach (var vertex in sortedVertices)
+                {
+                    if (!currentSet.Contains(vertex))
+                    {
+                        if (verticesInSet.All(v => _graph[v].Contains(vertex)))
+                        {
+                            var newSet = string.Join(",", verticesInSet.Append(vertex).OrderBy(v => v));
+                            newSets.Add(newSet);
+                        }
+                    }
+                }
+            }
+        } while (newSets.Count != 0);
+
+        var firstSet = currentSets.First();
+        return firstSet;
+    }
+
+    private HashSet<string> GetTriangles()
+    {
+        var results = new HashSet<string>();
+        foreach (var vertex in _vertices)
+        {
+            foreach (var secondVertex in _vertices)
+            {
+                foreach (var thirdVertex in _vertices)
+                {
+                    if (_graph[vertex].Contains(secondVertex) &&
+                        _graph[secondVertex].Contains(thirdVertex) &&
+                        _graph[thirdVertex].Contains(vertex))
+                    {
+                        results.Add(string.Join(",", new[] { vertex, secondVertex, thirdVertex }.OrderBy(v => v)));
+                    }
+                }
+            }
+        }
+
+        return results;
+    }
+}

src/AdventOfCode.Puzzles/2024/23/TestData.txt

@@ -0,0 +1,32 @@
+kh-tc
+qp-kh
+de-cg
+ka-co
+yn-aq
+qp-ub
+cg-tb
+vc-aq
+tb-ka
+wh-tc
+yn-cg
+kh-ub
+ta-co
+de-co
+tc-td
+tb-wq
+wh-td
+ta-ka
+td-qp
+aq-cg
+wq-ub
+ub-vc
+de-ta
+wq-aq
+wq-vc
+wh-yn
+ka-de
+kh-ta
+co-tc
+wh-qp
+tb-vc
+td-yn