diff --git a/YASI_12/YASI_12.vcxproj b/YASI_12/YASI_12.vcxproj
index d02ea45..8ca9c31 100644
--- a/YASI_12/YASI_12.vcxproj
+++ b/YASI_12/YASI_12.vcxproj
@@ -84,6 +84,7 @@
     <ClInclude Include="ds.comparable.h" />
     <ClInclude Include="ds.dictionary.h" />
     <ClInclude Include="ds.doublylinkedlist.h" />
+    <ClInclude Include="ds.hashtable.h" />
     <ClInclude Include="ds.iterator.h">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">false</ExcludedFromBuild>
     </ClInclude>
diff --git a/YASI_12/YASI_12.vcxproj.filters b/YASI_12/YASI_12.vcxproj.filters
index 8ab932c..f5945f1 100644
--- a/YASI_12/YASI_12.vcxproj.filters
+++ b/YASI_12/YASI_12.vcxproj.filters
@@ -95,5 +95,8 @@
     <ClInclude Include="test.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="ds.hashtable.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/YASI_12/ds.doublylinkedlist.h b/YASI_12/ds.doublylinkedlist.h
index 6e8c27f..f904df5 100644
--- a/YASI_12/ds.doublylinkedlist.h
+++ b/YASI_12/ds.doublylinkedlist.h
@@ -105,6 +105,7 @@ namespace ds{
 
 	public:
 		typedef DLLIterator<E, Node> iterator;
+		typedef node_t NodeType;
 		/////// constructor/destructor ///////////
 		DoublyLinkedList(){
 			// make a unit circle: horizon--horizon--horizon
diff --git a/YASI_12/ds.hashtable.h b/YASI_12/ds.hashtable.h
new file mode 100644
index 0000000..34ae839
--- /dev/null
+++ b/YASI_12/ds.hashtable.h
@@ -0,0 +1,238 @@
+#pragma once
+#include "common.h"
+#include "ds.kvpair.h"
+#include "ds.doublylinkedlist.h"
+using namespace std;
+
+namespace yasi{
+namespace ds{
+
+template<class Key, class Value = Key>
+class IKeyValueStore{
+public:
+	virtual ~IKeyValueStore(){}
+	virtual Value* get(const Key&) const = 0;
+	virtual void put(const Key&, const Value&) = 0;
+	virtual bool contains(const Key&) const = 0;
+	virtual void remove(const Key&) = 0;
+};
+
+template<class Key>
+class IHashFunction{
+public:
+	virtual int operator()(Key n) const = 0;
+};
+
+template<class Key>
+class IntHashFunction : public IHashFunction<Key>{
+public:
+	virtual int operator()(Key n) const override{
+		return n ^ (~n << 11) ^ (n << 3) ^ (~n << 27);
+	}
+};
+
+//template<class Bucket, class Key>
+//class ICollisionStrategy{
+//
+//public:
+//	virtual ~ICollisionResolutionStrategy(){}
+//	// either returns a ptr to the bucket-index, or NULL if no bucket found
+//	virtual int* findBucket(const Key& k, (void*)pHashTable) = 0;
+//};
+
+
+template<	class Key, 
+			class Value,
+			class BucketType,
+			class HashFunction
+>
+class HashTableBase : public IKeyValueStore < Key, Value >{
+protected:
+	// size of the table
+	// must be a power of two
+	unsigned int _size;
+	unsigned int _logSize;
+	// actual number of keys stored in the table
+	unsigned int _population;
+	// the buckets array
+	BucketType* table;
+	// the hash function
+	HashFunction hash;
+	inline int index(const Key& k) const{
+		return hash(k) & ((1 << _logSize) - 1); // hash(k) % _size 
+	}
+	BucketType& bucket(const Key& k) const{
+		return table[index(k)];
+	}
+public:
+	// the type of the entries in the hash table
+	HashTableBase():HashTableBase(6){}
+	HashTableBase(unsigned int logSize) : _logSize(logSize), _size(1 << logSize), _population(0){	
+		table = new BucketType[_size];
+		// initialize to zero
+		memset(table, 0, _size * sizeof(BucketType));
+	}
+	virtual ~HashTableBase(){ DELETE_ARR_SAFE(table); _size = _population = 0; }
+};
+
+
+// Separate chaining collision resolution strategy
+// each bucket holds a list of values mapped into that bucket
+template<	
+	class Key,
+	class Value = Key,
+	class HashFunction = IntHashFunction<int>,
+	class Pred = KVPairEqualityPredicate<Key> 
+>
+class SeparateChainingHashTable : public HashTableBase<
+	Key,
+	Value,
+	DoublyLinkedList< KVPair<Key,Value> >*,
+	HashFunction>
+{
+	///////////////// enable testing ///////////////////
+	friend class SeparateChainingHashTableTest;
+
+protected:
+	typedef KVPair<Key, Value> Pair;
+	typedef DoublyLinkedList < Pair > List;
+	typedef typename List::NodeType	Node;
+public:
+	typedef List* BucketType;
+protected:
+	// returns the pointer to the value if exists, otherwise returns NULL
+	Node* bucketNode(BucketType pList, const Key& k) const{
+		Pred keyEquals;
+		for (List::iterator n = pList->begin(); n != pList->end(); n++){
+			if (keyEquals((*n).key,k)){
+				// found node; 
+				return n.pNode;
+			}
+		}
+		return NULL;
+	}
+	Pair* bucketEntry(BucketType pList, const Key& k) const{
+		Pred keyEquals;
+		for (List::iterator n = pList->begin(); n != pList->end(); n++){
+			if (keyEquals((*n).key, k)){
+				// found node; 
+				return & (n.pNode->element);
+			}
+		}
+		return NULL;
+	}
+	bool bucketContains(BucketType pList, const Key& k) const{
+		Pred keyEquals;
+		for (List::iterator n = pList->begin(); n != pList->end(); n++){
+			if (keyEquals((*n).key, k)){
+				// found node; 
+				return true;
+			}
+		}
+		return false;
+	}
+public:
+	typedef Key		KeyType;
+	typedef Value	ValueType;
+
+	virtual ~SeparateChainingHashTable(){
+		if (table){
+			for (int i = 0; i < _size; i++){
+				// each entry is either NULL or a List*
+				if (table[i]){
+					table[i]->clear();
+					DELETE_SAFE(table[i]);
+				}
+			}
+		}
+	}
+	SeparateChainingHashTable() :SeparateChainingHashTable(6){}
+	SeparateChainingHashTable(unsigned int logSize) : HashTableBase(logSize){
+
+		//collisionHandler(this);
+	}
+	// returns true on success, false on failure
+	virtual void put(const Key& k, const Value& v) override{
+		int i = index(k);
+		BucketType pList = table[i];
+		if (pList == NULL){
+			// empty slot; create a new list
+			pList = new List();
+			// pushFront for better temporal locality
+			pList->pushFront(Pair(k, v));
+			_population++;
+		}
+		else{
+			// existing bucket
+			Pair* pEntry = bucketEntry(pList, k);
+			if (pEntry){
+				// key already exists; update value
+				pEntry->value = v;
+			}
+			else{
+				pList->pushFront(Pair(k, v));
+				_population++;
+			}
+		}
+	}
+	virtual Value* get(const Key& k) const override{
+		int i = index(k);
+		BucketType pList = table[i];
+		if (pList != NULL){
+			// existing bucket
+			Pair* pEntry = bucketEntry(pList, k);
+			if (pEntry)
+				return &pEntry->value;
+		}
+		return NULL;
+	}
+	virtual void remove(const Key& k) override{
+		int i = index(k);
+		BucketType pList = table[i];
+		if (pList == NULL){
+			// the key is absent
+			// nothing to do
+		}
+		else{
+			// existing bucket
+			Node* pNode = bucketNode(pList, k);
+			if (pNode){
+				pList->remove(pNode);
+				_population--;
+			}
+		}
+	}
+	virtual bool contains(const Key& k) const override{
+		int i = index(k);
+		BucketType pList = table[i];
+		if (pList != NULL){
+			// existing bucket
+			return bucketContains(pList,k);
+		}
+		return false;
+	}
+
+	int size(){ return _size; }
+	int population(){ return _population; }
+
+};
+
+class SeparateChainingHashTableTest : public yasi::Test{
+protected:
+	typedef SeparateChainingHashTable<int, int> IntHashTable;
+	typedef KVPair<int, int> Pair;
+	typedef IntHashTable::BucketType BucketType;
+
+	IntHashTable h;
+public:
+
+	void hashCode(){
+		// hashcode must be within range
+		ASSERT_LT(h.index(10), h.size()) << "index(10) out of range";
+	}
+};
+
+ADD_TEST_F(SeparateChainingHashTableTest, hashCode);
+
+} // namespace ds
+} // namespace yasi
\ No newline at end of file
diff --git a/YASI_12/ds.kvpair.h b/YASI_12/ds.kvpair.h
index 3118427..63989cc 100644
--- a/YASI_12/ds.kvpair.h
+++ b/YASI_12/ds.kvpair.h
@@ -33,5 +33,10 @@ namespace yasi{
 			return out;
 		}
 
-	}
-}
\ No newline at end of file
+template<class Key>
+class KVPairEqualityPredicate{
+public:
+	bool operator() (const Key& k1, const Key& k2){ return k1 == k2; }
+};
+	} // namespace ds
+}// namespace yasi
\ No newline at end of file
diff --git a/YASI_12/main.cpp b/YASI_12/main.cpp
index 137f34a..286f9ee 100644
--- a/YASI_12/main.cpp
+++ b/YASI_12/main.cpp
@@ -7,7 +7,7 @@
 #include "ds.binarysearchtree.h"
 #include "ds.priorityqueue.h"
 #include "ds.BSTDictionary.h"
-
+#include "ds.hashtable.h"
 //#include "Sorter.h"
 
 #include <cstdlib>