From 00aaa17bb6b25e8bdfe2605639b6d7aab9ceb16e Mon Sep 17 00:00:00 2001
From: Chris Cameron <chris.cameron@wedoresi.com>
Date: Fri, 16 Mar 2018 14:30:21 -0400
Subject: [PATCH] Adding GetClique and GetCliques recursion methods

---
 ICD.Common.Utils.Tests/RecursionUtilsTest.cs | 55 ++++++++++++++
 ICD.Common.Utils/RecursionUtils.cs           | 79 ++++++++++++++++++++
 2 files changed, 134 insertions(+)

diff --git a/ICD.Common.Utils.Tests/RecursionUtilsTest.cs b/ICD.Common.Utils.Tests/RecursionUtilsTest.cs
index f64c5f2..8a32c50 100644
--- a/ICD.Common.Utils.Tests/RecursionUtilsTest.cs
+++ b/ICD.Common.Utils.Tests/RecursionUtilsTest.cs
@@ -72,6 +72,61 @@ namespace ICD.Common.Utils.Tests
 			}
 		}
 
+		private static readonly Dictionary<int, IEnumerable<int>> s_CliqueGraph = new Dictionary<int, IEnumerable<int>>
+		{
+			{1, new[] {2, 3}},
+			{2, new[] {1, 4}},
+			{3, new[] {1}},
+			{4, new[] {2}},
+			{5, new[] {6}},
+			{6, new[] {5}}
+		};
+
+		[Test]
+		public void GetCliquesTest()
+		{
+			int[][] cliques =
+				RecursionUtils.GetCliques(s_CliqueGraph.Keys, i => s_CliqueGraph[i])
+				              .Select(c => c.ToArray())
+				              .ToArray();
+
+			Assert.AreEqual(2, cliques.Length);
+
+			int[] clique1 = cliques.FirstOrDefault(c => c.Contains(1));
+			int[] clique2 = cliques.FirstOrDefault(c => c != clique1);
+
+			Assert.NotNull(clique1);
+			Assert.NotNull(clique2);
+
+			Assert.AreEqual(4, clique1.Length);
+			Assert.IsTrue(clique1.Contains(1));
+			Assert.IsTrue(clique1.Contains(2));
+			Assert.IsTrue(clique1.Contains(3));
+			Assert.IsTrue(clique1.Contains(4));
+
+			Assert.AreEqual(2, clique2.Length);
+			Assert.IsTrue(clique2.Contains(5));
+			Assert.IsTrue(clique2.Contains(6));
+		}
+
+		[Test]
+		public void GetCliqueTest()
+		{
+			int[] clique = RecursionUtils.GetClique(s_CliqueGraph, 1).ToArray();
+
+			Assert.AreEqual(4, clique.Length);
+			Assert.IsTrue(clique.Contains(1));
+			Assert.IsTrue(clique.Contains(2));
+			Assert.IsTrue(clique.Contains(3));
+			Assert.IsTrue(clique.Contains(4));
+
+			clique = RecursionUtils.GetClique(s_CliqueGraph, 5).ToArray();
+
+			Assert.AreEqual(2, clique.Length);
+			Assert.IsTrue(clique.Contains(5));
+			Assert.IsTrue(clique.Contains(6));
+		}
+
 		[Test]
 		public void BreadthFirstSearchTest()
 		{
diff --git a/ICD.Common.Utils/RecursionUtils.cs b/ICD.Common.Utils/RecursionUtils.cs
index 7708a17..fe2a4fd 100644
--- a/ICD.Common.Utils/RecursionUtils.cs
+++ b/ICD.Common.Utils/RecursionUtils.cs
@@ -3,11 +3,90 @@ using System.Collections.Generic;
 using System.Linq;
 using ICD.Common.Properties;
 using ICD.Common.Utils.Collections;
+using ICD.Common.Utils.Extensions;
 
 namespace ICD.Common.Utils
 {
 	public static class RecursionUtils
 	{
+		/// <summary>
+		/// Returns a sequence of the cliques in the graph.
+		/// </summary>
+		/// <typeparam name="T"></typeparam>
+		/// <param name="nodes"></param>
+		/// <param name="getAdjacent"></param>
+		/// <returns></returns>
+		public static IEnumerable<IEnumerable<T>> GetCliques<T>(IEnumerable<T> nodes, Func<T, IEnumerable<T>> getAdjacent)
+		{
+			if (nodes == null)
+				throw new ArgumentNullException("nodes");
+
+			if (getAdjacent == null)
+				throw new ArgumentNullException("getAdjacent");
+
+			Dictionary<T, IEnumerable<T>> map = nodes.ToDictionary(n => n, getAdjacent);
+			IcdHashSet<T> visited = new IcdHashSet<T>();
+
+			return map.Keys
+			          .Where(n => !visited.Contains(n))
+			          .Select(node => GetClique(map, visited, node));
+		}
+
+		/// <summary>
+		/// Gets the clique containing the given node.
+		/// </summary>
+		/// <typeparam name="T"></typeparam>
+		/// <param name="map"></param>
+		/// <param name="node"></param>
+		/// <returns></returns>
+		public static IEnumerable<T> GetClique<T>(IDictionary<T, IEnumerable<T>> map, T node)
+		{
+			if (map == null)
+				throw new ArgumentNullException("map");
+
+// ReSharper disable once CompareNonConstrainedGenericWithNull
+			if (node == null)
+				throw new ArgumentNullException("node");
+
+			return GetClique(map, new IcdHashSet<T>(), node);
+		}
+
+		/// <summary>
+		/// Gets the clique containing the node.
+		/// </summary>
+		/// <typeparam name="T"></typeparam>
+		/// <param name="map"></param>
+		/// <param name="visited"></param>
+		/// <param name="node"></param>
+		/// <returns></returns>
+		private static IEnumerable<T> GetClique<T>(IDictionary<T, IEnumerable<T>> map, IcdHashSet<T> visited, T node)
+		{
+			if (map == null)
+				throw new ArgumentNullException("map");
+
+			if (visited == null)
+				throw new ArgumentNullException("visited");
+
+// ReSharper disable once CompareNonConstrainedGenericWithNull
+			if (node == null)
+				throw new ArgumentNullException("node");
+
+			if (visited.Contains(node))
+				yield break;
+
+			if (!map.ContainsKey(node))
+				yield break;
+
+			visited.Add(node);
+
+			yield return node;
+
+			IEnumerable<T> adjacent = map.GetDefault(node, Enumerable.Empty<T>());
+
+			foreach (T item in adjacent.SelectMany(a => GetClique(map, visited, a)))
+				yield return item;
+		}
+
 		/// <summary>
 		/// Returns all of the nodes in the tree via breadth-first search.
 		/// </summary>