diff --git a/YASI_12/ds.HopScotchHashTable.h b/YASI_12/ds.HopScotchHashTable.h
index e0b9d22..b1ab8c7 100644
--- a/YASI_12/ds.HopScotchHashTable.h
+++ b/YASI_12/ds.HopScotchHashTable.h
@@ -66,27 +66,30 @@ class HopScotchHashTable
 		base;
 
 
-	virtual void copyTable(BucketType* oldTable, const unsigned int oldSize) override{
-		base::copyTable(oldTable, oldSize);
-	}
-
-	// swap two bucket entries
-	void swap(const int bucketOne, const int bucketTwo) const{
-		EntryType temp = table[bucketOne];
-		table[bucketOne] = table[bucketTwo];
-		table[bucketTwo] = temp;
-	}
-
 	
 	//---------- HopScotch Properties/Methods ----------
 	static const unsigned int INIT_H = 4;
 	size_t H; // the neighborhood size
 	size_t _zeroKeyBucket; // the bucket containing (hashed) zero key
-	// we should find something within first H-1 trials
-	// if not found, returns NULL
-	BucketType* lookupRight(const int bucket, const Key& key){
+#if _DEBUG
+	int _numHops;
+#endif // _DEBUG
 
+
+public:
+
+	virtual ~HopScotchHashTable(){}
+	HopScotchHashTable(unsigned int logSize = INIT_LOGSIZE, unsigned int H = INIT_H) :H(H), IntLinearProbingHashTable(logSize){
+		assert(_size >= H);
+#if _DEBUG
+		_numHops = 0;
+#endif
 	}
+
+protected:
+
+	// we should find something within first H-1 trials
+	// if not found, returns NULL
 #if YASI_ALLOW_ZERO_KEY
 	virtual inline bool isNull(const int bucket) const{
 		if (table[bucket].key != 0){
@@ -113,6 +116,18 @@ class HopScotchHashTable
 	}
 #endif // YASI_ALLOW_ZERO_KEY
 
+
+	virtual void copyTable(BucketType* oldTable, const unsigned int oldSize) override{
+		base::copyTable(oldTable, oldSize);
+	}
+
+	// swap two bucket entries
+	void swap(const int bucketOne, const int bucketTwo) const{
+		EntryType temp = table[bucketOne];
+		table[bucketOne] = table[bucketTwo];
+		table[bucketTwo] = temp;
+	}
+
 	// push this entry to the right
 	// returns false if it is not possible to push
 	// returns true on success
@@ -179,6 +194,11 @@ class HopScotchHashTable
 	}
 
 	virtual BucketType* insertKey(const Key& k){
+		if (k == 0){
+			cerr << "HopScotchHashTable::insertKey(): key 0 is not allowed." << endl;
+			return NULL;
+		}
+
 		int firstBucket = index(k);
 		int cur = firstBucket;
 		int end = modSize(firstBucket + H);
@@ -208,15 +228,33 @@ class HopScotchHashTable
 	}
 
 	virtual BucketType* lookupKey(const Key& k){
+		if (k == 0){
+			cerr << "HopScotchHashTable::lookupKey(): key 0 is not allowed." << endl;
+			return NULL;
+		}
+
 		int firstBucket = index(k);
-		for (int i = 0; i < H; i++){
+#if _DEBUG
+		// keep track of how many hops till found
+		_numHops = 0;
+#endif
+		// keep probing to the right
+		for (int i = 0; ; i = circularNext(i) ){
 			if (table[firstBucket + i].key == k)
 				return &table[firstBucket + i];
+#if _DEBUG
+			else
+				_numHops++;
+#endif
 		}
 		return NULL;
 	}
 
 	virtual void removeKey(const Key& k){
+		if (k == 0){
+			cerr << "HopScotchHashTable::remove(): key 0 is not allowed." << endl;
+			return;
+		}
 		BucketType* pBucket = lookupKey(k);
 		if (pBucket){
 			pBucket->key = 0;
@@ -227,11 +265,6 @@ class HopScotchHashTable
 
 public:
 
-	virtual ~HopScotchHashTable(){}
-	HopScotchHashTable(unsigned int logSize = INIT_LOGSIZE, unsigned int H = INIT_H) :H(H),IntLinearProbingHashTable(logSize){
-		assert(_size >= H);
-	}
-
 };
 
 ////////// test IntLinearProbingHashTable
@@ -346,9 +379,6 @@ class HopScotchHashTableTest : public yasi::Test
 		}
 	}
 
-	void pushToRightOverZeroKey(){
-
-	}
 	void circularDiff(){
 		IntHashTable8 h(3,4);
 		ASSERT_EQ(8, h.size());
@@ -360,6 +390,33 @@ class HopScotchHashTableTest : public yasi::Test
 		ASSERT_EQ(7, h.circularDiff(4, 3));
 	}
 
+	void insertRemoveLookup(){
+		IntHashTable h(4, 4); // size 16, H=4
+		ASSERT_EQ(16, h.size());
+		ASSERT_EQ(0, h.population());
+		ASSERT_EQ(6, h.H);
+
+		// try to find an empty key
+		ASSERT_EQ(NULL, (int)h.lookupKey(7));
+		ASSERT_EQ(NULL, (int)h.lookupKey(0));
+
+		// insert one key, find it, and remove it
+		h.put(5, 50);
+		ASSERT_EQ(true, h.contains(5));
+		ASSERT_EQ(5, *h.lookupKey(5));
+		ASSERT_EQ(50, *h.get(5));
+		ASSERT_EQ(1, h.population());
+		ASSERT_EQ(16, h.population());
+		h.remove(5);
+		ASSERT_EQ(false, h.contains(5));
+		ASSERT_EQ(NULL, (int)h.lookupKey(5));
+		ASSERT_EQ(NULL, (int)h.get(5));
+		ASSERT_EQ(0, h.population());
+		ASSERT_EQ(16, h.population());
+
+		// insert many keys that 
+	}
+
 };
 ADD_TEST_F(HopScotchHashTableTest, circularDiff);
 ADD_TEST_F(HopScotchHashTableTest, pushToRight);