diff --git a/thu_dsa/chp3/List.h b/thu_dsa/chp3/List.h
new file mode 100644
index 0000000..67ad565
--- /dev/null
+++ b/thu_dsa/chp3/List.h
@@ -0,0 +1,221 @@
+#ifndef LIST_H_
+#define LIST_H_
+
+#include "ListNode.h"
+
+template <typename T>
+class List{
+private:
+	ListNodePosi(T) head;
+	ListNodePosi(T) tail;
+	int             size;
+
+protected:// internal methods
+
+
+public:
+	//constructors
+	List();									// empty List
+	List(List const &L);					// copy from another List
+	List(List const &L, int rank, int n);	// copy n elements from L[rank]
+	List(ListNodePosi(T) p, int n);			// copy n elements from position p
+
+	//deconstructor
+	~List();
+
+	//read-only interfaces
+	ListNodePosi(T) first() const { return head->succ; }
+	ListNodePosi(T) last() const { return tail->prev; }
+	ListNodePosi(T) find(T const &val) const { return find(val, size, tail); }		//find val from all elements of the list
+	ListNodePosi(T) find(T const &val, int n, ListNodePosi(T) p) const;				//find val from a range of n elements before p
+	T& operator[](int rank);
+	int getSize() const { return size; }
+	bool empty() const { return size == 0; }
+
+	//writable interfaces
+
+	//insert and delete operations
+	ListNodePosi(T) push_back(T const &val);
+	ListNodePosi(T) push_front(T const & val);
+	ListNodePosi(T) insert_before(int rank, T const &val);
+	ListNodePosi(T) insert_before(ListNodePosi(T) p, T const &val);
+	ListNodePosi(T) pop_back();
+	ListNodePosi(T) pop_front();
+	ListNodePosi(T) pop(int rank);
+	ListNodePosi(T) pop(ListNodePosi(T) p);
+
+	//deduplicate & uniquify
+	int deduplicate();
+	int uniquify();
+};
+
+/*----------implementations of class List----------*/
+
+//constructors
+template <typename T>
+List<T>::List(){
+	tail = new ListNode<T>();
+	head = new ListNode<T>();
+	tail->prev = head;
+	head->succ = tail;
+	size       = 0;
+}
+
+template <typename T>
+List<T>::List(List const &L) {
+	tail = new ListNode<T>();
+	head = new ListNode<T>();
+	tail->prev = head;
+	head->succ = tail;
+	size = 0;
+
+	ListNodePosi(T) p = L.head->succ;
+	for (int ix = 0, size = L.getSize(); ix != size; ++ix, p = p->succ)
+		push_back(p->val);
+}
+
+template <typename T>
+List<T>::List(List const &L, int rank, int n){
+	ListNodePosi(T) p = L.head->succ;
+	while (rank--) p = p->succ;
+	
+	tail = new ListNode<T>();
+	head = new ListNode<T>();
+	tail->prev = head;
+	head->succ = tail;
+	size = 0;
+
+	for (int ix = 0; ix != n; ++ix, p = p->succ)
+		push_back(p->val);
+}
+
+template <typename T>
+List<T>::List(ListNodePosi(T) p, int n){
+	tail = new ListNode<T>();
+	head = new ListNode<T>();
+	tail->prev = head;
+	head->succ = tail;
+	size = 0;
+
+	for (int ix = 0; ix != n; ++ix, p = p->succ)
+		push_back(p->val);
+}
+
+//deconstructor
+template <typename T>
+List<T>::~List(){
+	while (size) pop_back();
+}
+
+//read-only interfaces
+
+template <typename T>
+ListNodePosi(T) List<T>::find(T const &val, int n, ListNodePosi(T) p) const {
+	while ((p = p->prev) != head && n--)
+		if (p->val == val) return p;
+	return nullptr;
+}
+
+template <typename T>
+T& List<T>::operator[](int rank){
+	ListNodePosi(T) p = head->succ;
+	while (rank--) p = p->succ;
+	return p->val;
+}
+
+// writable interfaces
+
+//insert and delete operations
+template <typename T>
+ListNodePosi(T) List<T>::push_back(T const &val){
+	++size;
+	return tail->insertAsPred(val);
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::push_front(T const &val) {
+	++size;
+	return head->insertAsSucc(val);
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::pop_back() {
+	if (empty()) return nullptr;
+	
+	ListNodePosi(T) res = tail->prev;
+	res->prev->succ     = tail;
+	tail->prev          = res->prev;
+	--size;
+	return res;
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::pop_front() {
+	if (empty()) return nullptr;
+
+	ListNodePosi(T) res = head->succ;
+	head->succ          = res->succ;
+	res->succ->prev     = head;
+	--size;
+	return res;
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::insert_before(int rank, T const &val){
+	ListNodePosi(T) p = head->succ;
+	while (rank--) p = p->succ;
+	return insert_before(p, val);
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::insert_before(ListNodePosi(T) p, T const &val){
+	++size;
+	return p->insertAsPred(val);
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::pop(int rank){
+	if (rank >= size || rank < 0) return nullptr;
+
+	ListNodePosi(T) p = head->succ;
+	while (rank--) p = p->succ;
+	return pop(p);
+}
+
+template <typename T>
+ListNodePosi(T) List<T>::pop(ListNodePosi(T) p){
+	p->prev->succ = p->succ;
+	p->succ->prev = p->prev;
+	--size;
+	return p;
+}
+
+//deduplicate & uniquify
+template <typename T>
+int List<T>::deduplicate(){
+	int oldSize = size;
+	ListNodePosi(T) p = head->succ;
+	ListNodePosi(T) tmp;
+	for (; p != tail; p = p->succ){
+		for(tmp = head->succ; tmp != p; tmp = tmp->succ){
+			if(tmp->val == p->val){
+				pop(tmp);
+				break;
+			}
+		}
+	}
+	return oldSize - size;
+}
+
+template <typename T>
+int List<T>::uniquify(){
+	if (empty()) return 0;
+
+	int oldSize = size;
+	ListNodePosi(T) p = head->succ;
+	while ((p = p->succ) != tail)
+		if (p->val == p->prev->val) pop(p);
+	return oldSize - size;
+}
+
+#endif
diff --git a/thu_dsa/chp3/ListNode.h b/thu_dsa/chp3/ListNode.h
new file mode 100644
index 0000000..f06a9b6
--- /dev/null
+++ b/thu_dsa/chp3/ListNode.h
@@ -0,0 +1,55 @@
+#ifndef LISTNODE_H_
+#define LISTNODE_H_
+
+#define ListNodePosi(T) ListNode<T>* 
+
+template <typename T>
+class ListNode{
+public:
+	ListNodePosi(T) prev;
+	ListNodePosi(T) succ;
+	T               val;
+
+	//constructor
+	ListNode();
+	ListNode(T val, ListNodePosi(T) const &p = nullptr, ListNodePosi(T) const &s = nullptr);
+
+	//external interfaces
+	ListNodePosi(T) insertAsPred(T const &val);
+	ListNodePosi(T) insertAsSucc(T const &val);
+};
+
+/*----------implementation of class ListNode----------*/
+
+//constructor
+template <typename T>
+ListNode<T>::ListNode(){
+	prev = nullptr;
+	succ = nullptr;
+}
+
+template <typename T>
+ListNode<T>::ListNode( T v, ListNodePosi(T) const &p = nullptr, ListNodePosi(T) const &s = nullptr ){
+	val  = v;
+	prev = p;
+	succ = s;
+}
+
+//external interfaces
+template <typename T>
+ListNodePosi(T) ListNode<T>::insertAsPred(T const &val){
+	ListNodePosi(T) newNode = new ListNode<T>(val, prev, this);
+	prev->succ = newNode;
+	prev = newNode;
+	return newNode;
+}
+
+template <typename T>
+ListNodePosi(T) ListNode<T>::insertAsSucc(T const &val){
+	ListNodePosi(T) newNode = new ListNode(val, this, succ);
+	succ->prev = newNode;
+	succ = newNode;
+	return newNode;
+}
+
+#endif
diff --git a/thu_dsa/chp3/test_list.cpp b/thu_dsa/chp3/test_list.cpp
new file mode 100644
index 0000000..6439d3a
--- /dev/null
+++ b/thu_dsa/chp3/test_list.cpp
@@ -0,0 +1,142 @@
+#include "List.h"
+#include <iostream>
+#include <cassert>
+using std::cout;
+using std::endl;
+
+void test_constructor1();
+void test_constructor2();
+void test_push();
+void test_pop();
+void test_find();
+void test_deduplicate();
+void test_uniquify();
+
+int main(){
+	cout << "Running tests......" << endl;
+	test_constructor1();
+	test_constructor2();
+	test_push();
+	test_pop();
+	test_find();
+	test_deduplicate();
+	test_uniquify();
+
+	cout << "All tests passed." << endl;
+	system("pause");
+	return 0;
+}
+
+void test_constructor1(){
+	List<double> l;
+	assert(l.getSize() == 0);
+	assert(l.empty());
+}
+
+void test_constructor2(){
+	List<int> l1;
+	int i[] = { 5,6,8,9,7,3,4,1,2,0 };
+	for (int ix = 0; ix != 10; ix++)
+		l1.push_back(i[ix]);
+
+	List<int> l2(l1);
+	for (int ix = 0; ix != 10; ix++)
+		assert(l2[ix] == i[ix]);
+
+	List<int> l4(l1.first(), 5);
+	for (int ix = 0; ix != 5; ix++)
+		assert(l4[ix] == i[ix]);
+	assert(l4.getSize() == 5);
+
+	List<int> l5(l1.last(), 1);
+	assert(l5.getSize() == 1);
+	assert(l5.first()->val == 0);
+
+	List<int> l3(l1, 3, 6);
+	assert(l3.getSize() == 6);
+	for (int ix = 0; ix != 6; ix++)
+		assert(l3[ix] == i[3+ix]);
+}
+
+void test_push(){
+	List<double> l;
+	double d[] = { 1.2, 3.4, 5.6, 7.8, 9.0 };
+	for (int ix = 0; ix != 5; ix++)
+		l.push_back(d[ix]);
+	for (int ix = 0; ix != 5; ix++)
+		assert(l[ix] == d[ix]);
+
+	List<int> l1;
+	int i[] = { 5,6,8,9,7,3,4,1,2,0 };
+	for (int ix = 0; ix != 10; ix++)
+		l1.push_front(i[ix]);
+	for (int ix = 0; ix != 10; ix++)
+		assert(l1[ix] == i[9-ix]);
+
+	//test insert_before
+	assert(l1.insert_before(0, 12)->val == 12);
+	assert(l1.getSize() == 11);
+	assert(l1.insert_before(11, 14)->val == 14);
+	assert(l1.getSize() == 12);
+}
+
+void test_pop(){
+	List<int> l1;
+	int i[] = { 5,6,8,9,7,3,4,1,2,0 };
+	for (int ix = 0; ix != 10; ix++)
+		l1.push_back(i[ix]);
+
+	assert(l1.pop_back()->val == 0);
+	assert(l1.pop_back()->val == 2);
+	assert(l1.pop_front()->val == 5);
+	assert(l1.pop_front()->val == 6);
+	assert(l1.getSize() == 6);
+
+	assert(l1.pop(3)->val == 3);
+	assert(l1.pop(5) == nullptr);
+	ListNodePosi(int) p = l1.first();
+	assert(l1.pop(p)->val == 8);
+}
+
+void test_find(){
+	List<int> l1;
+	int i[] = { 5,6,8,9,7,3,4,1,2,0 };
+	for (int ix = 0; ix != 10; ix++)
+		l1.push_back(i[ix]);
+
+	assert(l1.find(8)->val == 8);
+	assert(l1.find(7)->val == 7);
+	assert(l1.find(12) == nullptr);
+
+	assert(l1.find(7, 5, l1.last())->val == 7);
+	assert(l1.find(7, 4, l1.last()) == nullptr);
+}
+
+void test_deduplicate(){
+	List<int> l1;
+	int i[] = { 5,6,8,9,7,3,4,1,2,0};
+	for (int ix = 0; ix != 10; ix++) {
+		l1.push_front(i[ix]);
+		l1.push_back(i[ix]);
+	}
+
+	assert(l1.getSize() == 20);
+	assert(l1.deduplicate() == 10);
+	assert(l1.getSize() == 10);
+	for (int ix = 0; ix != 10; ix++)
+		assert(l1[ix] == i[ix]);
+}
+
+void test_uniquify(){
+	List<int> l1;
+	int i[] = {5,8,12,14,15,19,20,22,29,36};
+	for (int ix = 0; ix != 11; ix++) {
+		l1.push_back(i[ix]);
+		l1.push_back(i[ix]);
+	}
+	
+	assert(l1.getSize() == 22);
+	assert(l1.uniquify() == 11);
+	for (int ix = 0; ix != 11; ix++)
+		assert(l1[ix] == i[ix]);
+}