diff --git a/.idea/modules.xml b/.idea/modules.xml
index 88e9223..cc4f015 100644
--- a/.idea/modules.xml
+++ b/.idea/modules.xml
@@ -4,6 +4,7 @@
+
\ No newline at end of file
diff --git a/lecture/.idea/$PROJECT_FILE$ b/lecture/.idea/$PROJECT_FILE$
new file mode 100644
index 0000000..58b7e3e
--- /dev/null
+++ b/lecture/.idea/$PROJECT_FILE$
@@ -0,0 +1,11 @@
+
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\ No newline at end of file
diff --git a/lecture/.idea/.gitignore b/lecture/.idea/.gitignore
new file mode 100644
index 0000000..52769a9
--- /dev/null
+++ b/lecture/.idea/.gitignore
@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Datasource local storage ignored files
+/../../../../../../../../:\Users\lizi2\Desktop\python_reptile_practice\UC_Berkeley_CS61B\lecture\.idea/dataSources/
+/dataSources.local.xml
+# Editor-based HTTP Client requests
+/httpRequests/
diff --git a/lecture/.idea/checkstyle-idea.xml b/lecture/.idea/checkstyle-idea.xml
new file mode 100644
index 0000000..121d4a2
--- /dev/null
+++ b/lecture/.idea/checkstyle-idea.xml
@@ -0,0 +1,16 @@
+
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+
\ No newline at end of file
diff --git a/lecture/.idea/misc.xml b/lecture/.idea/misc.xml
new file mode 100644
index 0000000..881809e
--- /dev/null
+++ b/lecture/.idea/misc.xml
@@ -0,0 +1,15 @@
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\ No newline at end of file
diff --git a/lecture/.idea/modules.xml b/lecture/.idea/modules.xml
new file mode 100644
index 0000000..f008c2e
--- /dev/null
+++ b/lecture/.idea/modules.xml
@@ -0,0 +1,8 @@
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\ No newline at end of file
diff --git a/lecture/.idea/qaplug_profiles.xml b/lecture/.idea/qaplug_profiles.xml
new file mode 100644
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+++ b/lecture/.idea/qaplug_profiles.xml
@@ -0,0 +1,465 @@
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diff --git a/lecture/.idea/vcs.xml b/lecture/.idea/vcs.xml
new file mode 100644
index 0000000..6c0b863
--- /dev/null
+++ b/lecture/.idea/vcs.xml
@@ -0,0 +1,6 @@
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\ No newline at end of file
diff --git a/lecture/out/production/lecture/IntList.class b/lecture/out/production/lecture/IntList.class
new file mode 100644
index 0000000..fcc71ef
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diff --git a/lecture/out/production/lecture/SList$IntNode.class b/lecture/out/production/lecture/SList$IntNode.class
new file mode 100644
index 0000000..95e4ae2
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diff --git a/lecture/out/production/lecture/SList.class b/lecture/out/production/lecture/SList.class
new file mode 100644
index 0000000..19b8051
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diff --git a/lecture/out/production/lecture/lecture2_1.class b/lecture/out/production/lecture/lecture2_1.class
new file mode 100644
index 0000000..8cb8b1c
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diff --git a/lecture/out/production/lecture/lecture2_2.class b/lecture/out/production/lecture/lecture2_2.class
new file mode 100644
index 0000000..dc2977a
Binary files /dev/null and b/lecture/out/production/lecture/lecture2_2.class differ
diff --git a/lecture/out/production/lecture/lecture2_4.class b/lecture/out/production/lecture/lecture2_4.class
new file mode 100644
index 0000000..d3dc4dc
Binary files /dev/null and b/lecture/out/production/lecture/lecture2_4.class differ
diff --git "a/lecture_2_\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md" "b/lecture_2_\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md"
new file mode 100644
index 0000000..dfdf83a
--- /dev/null
+++ "b/lecture_2_\346\234\252\345\256\214\346\210\220\347\232\204\344\273\273\345\212\241.md"
@@ -0,0 +1,5 @@
+# 双向链表（Intnode中的prev指针）（project1 待完成）
+
+# DList中会使用泛型，还没搞明白
+
+# Lecture2_1 guide中如何不使用new操作符，就使得L的每个元素都加1，还不改变原来L的值？
\ No newline at end of file
diff --git a/lecture_guide/lecture_guide.iml b/lecture_guide/lecture_guide.iml
new file mode 100644
index 0000000..28ac7fd
--- /dev/null
+++ b/lecture_guide/lecture_guide.iml
@@ -0,0 +1,16 @@
+
+
+
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+
\ No newline at end of file
diff --git a/lecture_guide/src/IntNode.java b/lecture_guide/src/IntNode.java
new file mode 100644
index 0000000..3a45642
--- /dev/null
+++ b/lecture_guide/src/IntNode.java
@@ -0,0 +1,50 @@
+/**
+ * @author Li Zezhong
+ * @create 2021-12-07 21:58
+ */
+public class IntNode {
+ public int first;
+ public IntNode rest;
+
+ public IntNode(int f, IntNode r) {
+ first = f;
+ rest = r;
+ }
+
+ /** Return the size of the list using... recursion! */
+ public int size() {
+ if(rest ==null){
+ return 1;
+ }
+ return 1+rest.size();
+ }
+
+ /** Return the size of the list using no recursion! */
+ public int iterativeSize() {
+ IntNode p = this;
+ int size = 1;
+ while(p.rest != null){
+ size +=1;
+ p = p.rest;
+ }
+ return size;
+ }
+
+ /** Returns the ith value in this list.*/
+ public int get(int i) {
+ if(i==0){
+ return first;
+ }
+ return rest.get(i-1);
+ }
+
+ public static void main(String[] args) {
+ IntNode L = new IntNode(15, null);
+ L = new IntNode(10, L);
+ L = new IntNode(5, L);
+
+// System.out.println(L.iterativeSize());
+// System.out.println(L.get(0));
+ System.out.println(L.iterativeSize());
+ }
+}
diff --git a/lecture_guide/src/Lists1Exercises.java b/lecture_guide/src/Lists1Exercises.java
new file mode 100644
index 0000000..a62cf04
--- /dev/null
+++ b/lecture_guide/src/Lists1Exercises.java
@@ -0,0 +1,65 @@
+/**
+ * @author Li Zezhong
+ * @create 2021-12-07 20:15
+ */
+public class Lists1Exercises {
+ /** Returns an IntList identical to L, but with
+ * each element incremented by x. L is not allowed
+ * to change. */
+ public static IntNode incrList(IntNode L, int x) {
+ /* Your code here. */
+ int i=L.size()-1;
+ IntNode p=new IntNode(L.get(i)+x,null);
+ while(i>0){
+ i -=1;
+ p = new IntNode(L.get(i)+x,p);
+ }
+ return p;
+ }
+
+
+ /** Returns an IntList identical to L, but with
+ * each element incremented by x. Not allowed to use
+ * the 'new' keyword. */
+ public static IntNode dincrList(IntNode L, int x) {
+ IntNode p = L;
+ while(p !=null){
+ p.first -=x;
+ p = p.rest;
+ }
+ return L;
+ }
+
+ public static void main(String[] args) {
+ IntNode L = new IntNode(5, null);
+ L.rest = new IntNode(7, null);
+ L.rest.rest = new IntNode(9, null);
+
+// System.out.println(L.size());
+// System.out.println(L.iterativeSize());
+
+ // Test your answers by uncommenting. Or copy and paste the
+ // code for incrList and dincrList into IntList.java and
+ // run it in the visualizer.
+// System.out.println(L.get(1));
+ IntNode p = Lists1Exercises.incrList(L,2);
+ int i=0;
+// System.out.println(p.size());
+ while(i