Add DisjointSet

Author: Colin Lin

Algon/Algon.vcxproj

@@ -64,6 +64,7 @@
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
+    <ClInclude Include="dstruct\DisjointSet.h" />
     <ClInclude Include="dstruct\SkipList.h" />
   </ItemGroup>
   <ItemGroup>

Algon/Algon.vcxproj.filters

@@ -18,6 +18,9 @@
     <ClInclude Include="dstruct\SkipList.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="dstruct\DisjointSet.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="Example.cpp">

Algon/dstruct/DisjointSet.h

@@ -0,0 +1,121 @@
+#pragma once
+#include <set>
+#include <memory>
+#include <unordered_map>
+#include <initializer_list>
+#include <stdexcept>
+#include <assert.h>
+namespace colinli {
+namespace algon {
+
+  template<typename T>
+  using uPtr = std::shared_ptr<T>;
+  template<typename T>
+  using Set = std::set < T > ;
+  template <typename K, typename V>
+  using HashMap = std::unordered_map < K, V > ;
+
+  template<typename TKey>
+  class DisjointSets
+  {     
+  private:
+    Set<TKey> keys_;
+    HashMap<TKey, TKey> parent_;
+    HashMap<TKey, int> rank_;
+  public:
+    DisjointSets(){}
+    DisjointSets(std::initializer_list<TKey> keys):
+      keys_(keys)
+    {
+      for (auto k : keys_)
+      {
+        parent_[k] = k;
+        rank_[k] = 1;
+      }    
+    }    
+    /// <summary>
+    /// Unions two elements 
+    /// </summary>
+    void Union(TKey x, TKey y)
+    {
+      linkRoot(*FindSet(x), *FindSet(y));
+    }
+    
+    /// <summary>
+    /// Unions more than two elements
+    /// </summary>
+    template <typename TKey, typename... TRest >
+    void Union(TKey x, TKey y, TRest... rest)
+    {
+      Union(x, y);
+      Union(y, rest...);
+    }
+
+    bool Contains(TKey x) const 
+    {
+      return keys_.count(x) != 0;
+    }
+    
+    /// <summary>
+    /// Finds the set representative (root) for given element x
+    /// </summary>
+    /// <param name="x">input element</param>
+    /// <returns>the pointer to root of the set to which x belongs</returns>
+    TKey* FindSet(TKey x)
+    {
+      if (parent_.count(x) == 0)
+      {
+        return nullptr;
+      }
+      while (parent_[x] != x)
+      {
+        x = *FindSet(parent_[x]);
+      }
+      return &x;
+    }    
+    /// <summary>
+    /// Test connectivity of two elements
+    /// </summary>
+    /// <returns>true if the two elements are connected</returns>
+    bool Connected(TKey x, TKey y)
+    {
+      if (parent_.count(x) == 0 || parent_.count(y) == 0)
+      {
+        return false;
+      }
+      return FindSet(x) == FindSet(y);
+    }
+
+    void Add(TKey x)
+    {
+      keys_.insert(x);
+      parent_[x] = x;
+      rank_[x] = 1;
+    }
+
+  private:
+    // x and y are two roots to be linked
+    void linkRoot(TKey x, TKey y)
+    {
+      assert(parent_[x] == x && parent_[y] == y);
+      if (x == y)
+      {
+        return;
+      }
+      if (rank_[x] < rank_[y])
+      {
+        parent_[x] = y;
+      }
+      else
+      {
+        parent_[y] = x;
+      }
+      if (rank_[x] == rank_[y])
+      {
+        ++rank_[y];
+      }
+    }
+  };
+ 
+}//end of algon ns
+}// end of colinli ns

tests/DisjointSetTest.cpp

@@ -0,0 +1,46 @@
+#include "stdafx.h"
+#include "CppUnitTest.h"
+
+using namespace Microsoft::VisualStudio::CppUnitTestFramework;
+using namespace colinli::algon;
+namespace tests
+{
+	TEST_CLASS(DisjointSetTest)
+	{
+	public:
+    DisjointSets<int> iset;
+    TEST_METHOD_INITIALIZE(InitializeSet)
+    {
+      for (int i = 0; i < 10; i++)
+      {
+        iset.Add(i);
+      }
+    }
+
+		TEST_METHOD(TestContains)
+		{
+      Assert::IsTrue(iset.Contains(2));
+		}
+    TEST_METHOD(TestUnion)
+    {
+      iset.Union(1, 2);
+      iset.Union(2, 5);
+      iset.Union(3, 5);
+      Assert::IsTrue(iset.Connected(1, 2));
+      Assert::IsTrue(iset.Connected(1, 5));
+      Assert::IsTrue(iset.Connected(1, 3));
+      Assert::IsTrue(iset.Connected(2, 3));
+    }
+
+    TEST_METHOD(TestMultiUnion)
+    {
+      iset.Union(1, 2, 3, 4);
+      iset.Union(2, 7);
+      Assert::IsTrue(iset.Connected(1, 7));
+      Assert::IsTrue(iset.Connected(4, 7));
+      Assert::IsTrue(iset.Connected(4, 3));
+    }
+     
+
+	};
+}

tests/stdafx.h

@@ -11,4 +11,5 @@
 #include "CppUnitTest.h"
 #include <string>
 // TODO: reference additional headers your program requires here
-#include "../Algon/dstruct/SkipList.h"
+#include "../Algon/dstruct/SkipList.h"
+#include "../Algon/dstruct/DisjointSet.h"

tests/tests.vcxproj

@@ -86,6 +86,7 @@
     <ClInclude Include="targetver.h" />
   </ItemGroup>
   <ItemGroup>
+    <ClCompile Include="DisjointSetTest.cpp" />
     <ClCompile Include="stdafx.cpp">
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Create</PrecompiledHeader>
       <PrecompiledHeader Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">Create</PrecompiledHeader>

tests/tests.vcxproj.filters

@@ -29,5 +29,8 @@
     <ClCompile Include="SkiplistTests.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="DisjointSetTest.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>