diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e43b0f9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.DS_Store
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..38e7ff3
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "HW0/GreatestCommonDivisor"]
+	path = HW0/GreatestCommonDivisor
+	url = https://github.com/stevengogogo/GreatestCommonDivisor
+[submodule "HW0/NonogramSolver"]
+	path = HW0/NonogramSolver
+	url = https://github.com/stevengogogo/NonogramSolver
diff --git a/HW0/GreatestCommonDivisor b/HW0/GreatestCommonDivisor
new file mode 160000
index 0000000..e51b82d
--- /dev/null
+++ b/HW0/GreatestCommonDivisor
@@ -0,0 +1 @@
+Subproject commit e51b82d033a761138315dc0a971f85cf64c982d8
diff --git a/HW0/NonogramSolver b/HW0/NonogramSolver
new file mode 160000
index 0000000..99ab2ed
--- /dev/null
+++ b/HW0/NonogramSolver
@@ -0,0 +1 @@
+Subproject commit 99ab2ed0f24dafbccff7c41aaf7b9c9f35a4bf07
diff --git a/HW0/Pointers/README.md b/HW0/Pointers/README.md
new file mode 100644
index 0000000..9d7db65
--- /dev/null
+++ b/HW0/Pointers/README.md
@@ -0,0 +1,258 @@
+# Prolem 3 - *(Human Compiler)(Hand-written)
+
+## Problem 3a: Swaps two arrays using pointers
+
+![Screen Shot 2021-03-07 at 8 34 25 AM](https://user-images.githubusercontent.com/29009898/110225352-efdec580-7f1f-11eb-9675-516acb605e42.png)
+
+
+```c
+int fake_a[] = {1,3};
+int fake_b[] = {2,4};
+int *real_a = fake_a;
+int *real_b = fake_b;
+
+for(int i=0;i<2;i++)
+    printf("%d", *(real_a + i));
+for(int i=0;i<2;i++)
+    printf("%d", *(real_b + i));
+
+int *tmp = real_a; //tmp is a pointer to pointer
+real_b = fake_a;  // fill the blanks
+real_a = fake_b;  // fil the blanks
+
+for(int i=0;i<2;i++)
+    printf("%d", *(real_a + i));
+for(int i=0;i<2;i++)
+    printf("%d", *(real_b + i));
+```
+
+Test at: https://onlinegdb.com/SJ4JFi-7_
+
+![](img/Problem3a.png)
+
+---
+
+## Problem 3b: An array supporting negative indices
+
+![Screen Shot 2021-03-07 at 9 17 08 AM](https://user-images.githubusercontent.com/29009898/110226009-f7a16880-7f25-11eb-81db-7c27eb264c33.png)
+
+```c
+#include <stdio.h>
+#define MINN -50
+#define MAXN 50
+
+int main(){
+    int storage[MAXN - MINN + 1] = {0}; // 101
+    int *ary = storage - MINN ; //fill the blank
+
+    for(int i=MINN;i<=MAXN;i++)
+        ary[i] = i;
+    for(int i=MINN;i<=MAXN;i++)
+        printf("%d", ary[i]);
+    return 0;
+}
+```
+Verified at: https://onlinegdb.com/rydhl3W7u
+
+![](img/Problem3b.png)
+
+---
+
+## Problem 3C: Tranverses data nodes in a linked list.
+
+![Screen Shot 2021-03-07 at 12 03 34 PM](https://user-images.githubusercontent.com/29009898/110228580-38f14280-7f3d-11eb-9891-65aeaeb849e0.png)
+
+```c
+#include <stdio.h>
+#include <stdlib.h> //malloc / free
+#include <memory.h> //memset
+
+//use typedef to define "struct node" as "node"
+typedef struct node{
+    int data;
+    struct node *nxt;
+} node;
+
+node* alloc(int data, node* nxt){
+    node *tmp = (node*)malloc(sizeof(node));
+    tmp->data=data;
+    tmp->nxt = nxt;
+    return tmp;
+}
+
+void destroy(node *head){
+    if(head != NULL){ //FIll the blank 
+        destroy(head->nxt);
+        //clean sensitive data;
+        memset(head,0,sizeof(head));
+        free(head);
+    }
+}
+
+int main(){
+    // create nodes [0,1,2,4]
+    node* head = alloc(0, alloc(1,alloc(2,alloc(4,NULL))));
+    node* tmp = head;
+    //print the nodes subsequently
+    while(tmp!=NULL){
+        printf("%d -> ", *tmp-> data ); //FIll the blank 
+        tmp = (*tmp)->nxt; //FIll the blank 
+    }
+    printf("NULL");
+
+    //free the nodes subsequently to avoid memory leak
+    destroy(head);
+    return 0;
+}
+```
+
+### Curate
+
+Use `temp->data` not `(*tmp)->data`
+
+#### Copy a pointer to another pointer
+
+![Screen Shot 2021-03-07 at 12 31 17 PM](https://user-images.githubusercontent.com/29009898/110229016-09dcd000-7f41-11eb-9414-77bad043e4c8.png)
+> From [Basics of C Programmin](https://computer.howstuffworks.com/c24.htm)
+
+### Question 
+
+Wrong version: https://www.onlinegdb.com/
+Corrected version: https://onlinegdb.com/BkReV0bXd
+
+---
+
+## Problem 3D: Binary Tree
+![Screen Shot 2021-03-07 at 11 52 38 AM](https://user-images.githubusercontent.com/29009898/110228385-9f756100-7f3b-11eb-92e7-76ee4bf3413f.png)
+![Screen Shot 2021-03-07 at 11 52 48 AM](https://user-images.githubusercontent.com/29009898/110228386-a603d880-7f3b-11eb-9108-fb2e0b11d480.png)
+
+**問題**: `printf` 應該在 `if` 前面
+
+```c
+#include <stdio.h>
+#include <stdlib.h> //malloc /free
+#include <memory.h> //memset
+
+//use typedef to substitute "struct node with "node""
+typedef struct node {
+    int data;
+    struct node *left, *right;
+} node;
+
+//creates a node filledwith predefined values
+node* alloc(int data, node *left, node *right){
+    node *tmp = (node*)malloc(sizeof(node));
+    tmp->data = data,
+    tmp->left = left;
+    tmp->right = right;
+    return tmp;
+}
+
+//traverses (遍歷) the nodes recursively
+void traverse(node* root){
+    printf("%d", root->data);
+    if ((root->left != NULL) & (root->right != NULL)){
+        traverse(root->left);
+        traverse(root->right);
+    }
+}
+
+//frees the nodes recursively
+void destroy(node *root){
+    if ((root->left != NULL) & (root->right!=NULL)){
+        destroy(root->left);
+        destroy(root->right);
+        //clean sensitive data
+        memset(root, 0, sizeof(root));
+        free(root);
+    }
+}
+
+int main(){
+    // creates a hierarchical data structure
+    node *root = \
+        alloc(0,
+            alloc(3,
+                alloc(7, NULL, NULL),
+                alloc(4, NULL, NULL)
+            ),
+            alloc(2,
+                alloc(1, NULL, NULL),
+                alloc(9, NULL, NULL)
+            )
+        );
+
+    traverse(root);
+    destroy(root);
+}
+```
+Verify at: https://onlinegdb.com/r1VxlA-7d
+![](img/Problem3c.png)
+
+---
+
+## Notes
+
+### Null Pointer and `Segmentation fault`
+
+- Segmentation fault: 
+    > Segmentation fault is a specific kind of error caused by accessing memory that “does not belong to you
+- NULL Pointer
+    > People assign NULL to pointer to indicate that it points to nothing.
+
+### Read Only String and its Dynamical type
+
+- `char* str` Read only: able to share among functions
+    ```c
+    char *str = "gfg"; 
+    ```
+    Read only. `str[0]=a` leads to segmentation fault. Noted that read-only string can be passed among functions:
+    ```c
+    char *getString(){
+    char *str = "GfG"; /* Stored in read only part of shared segment */
+
+    /* No problem: remains at address str after getString() returns*/
+    return str; 
+    }	 
+
+    int main(){
+    printf("%s", getString()); 
+    getchar();
+    return 0;
+    }
+
+    ```
+- `char str[]` Mutable string: unable to share among functions.
+    ```c
+    int main(){
+        char str[];
+        str = "gfg";
+    }
+    ```
+- Store in heap: allow to share and modify
+    ```c
+    char *getString()
+    {
+    int size = 4;
+    char *str = (char *)malloc(sizeof(char)*size); /*Stored in heap segment*/
+    *(str+0) = 'G'; 
+    *(str+1) = 'f';  
+    *(str+2) = 'G';
+    *(str+3) = '\0';  
+    
+    /* No problem: string remains at str after getString() returns */   
+    return str;  
+    }     
+    int main()
+    {
+    printf("%s", getString());  
+    getchar();
+    return 0;
+    }
+    ```
+
+---
+## Reference
+1. Segmentation fault and pointer. [[stackoverflow](https://stackoverflow.com/questions/17873561/pointer-initialisation-gives-segmentation-fault)]
+2. String and storage. [[GreekforGeek](https://www.geeksforgeeks.org/storage-for-strings-in-c/)]
+3. Pointing to the same address. [[eBook-Basics of C Programming](https://computer.howstuffworks.com/c24.htm)]
\ No newline at end of file
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diff --git a/HW0/Problem_1/README.md b/HW0/Problem_1/README.md
deleted file mode 100644
index f1e3da6..0000000
--- a/HW0/Problem_1/README.md
+++ /dev/null
@@ -1,6 +0,0 @@
-# Problem 1: Greatest Common Divisor of Big Integers (Programming)
-
-
-
-## Reference
-1. BigInt in C [[gist](https://gist.github.com/bloopletech/338338)]
diff --git a/HW0/Problem_1/bigint.c b/HW0/Problem_1/bigint.c
deleted file mode 100644
index 479f545..0000000
--- a/HW0/Problem_1/bigint.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include<stdio.h>
-#include<string.h>
-#include<stdlib.h>
-#include "bigint.h"
-
-
-bigint* newnumc(char* numb)
-{
-    //allocate storage for the bigint
-    bigint* num = (bigint*)malloc(sizeof(bigint));
-
-    int numbl = strlen(numb);
-    int numbll = numbl-1;
-    
-}
\ No newline at end of file
diff --git a/HW0/Problem_1/bigint.h b/HW0/Problem_1/bigint.h
deleted file mode 100644
index 10db9c1..0000000
--- a/HW0/Problem_1/bigint.h
+++ /dev/null
@@ -1,10 +0,0 @@
-# define CHARZERO_ABOVEINTZERO 48
-
-typedef unsigned char digit; 
-
-typedef struct 
-{
-    digit* number;
-    int length;
-} bigint; 
-
diff --git a/HW0/Problem_1/main.c b/HW0/Problem_1/main.c
deleted file mode 100644
index 53c5fdf..0000000
--- a/HW0/Problem_1/main.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <stdio.h>
diff --git a/README.md b/README.md
index 60cfe4d..23ca385 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,40 @@
 # Data Structures 2021 Spring
+
+## Course Website
+
+
+## How to use `gitsubmodule`
+
+
+Show status
+-----------
+
+```bash
+git submodule status --recursive
+```
+
+Update all submodule
+--------------------
+
+#### Add project
+
+```bash
+# Clone to the current folder: 
+git submodule add <repository> 
+git submodule init
+
+```
+
+#### Fetch
+```bash
+git submodule update --recursive
+```
+
+#### Pull
+```bash
+git pull --recurse-submodules
+```
+
+## Plotting with [diagrams](https://app.diagrams.net/)
+
+[Diagram](https://app.diagrams.net/) features uploading to Github repository, making the drawing up-to-date easily!
\ No newline at end of file
diff --git a/assets/Screen_Shot_2021-03-02_at_1.53.11_PM.png b/assets/Screen_Shot_2021-03-02_at_1.53.11_PM.png
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diff --git a/docs/.nojekyll b/docs/.nojekyll
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index 0000000..e69de29
diff --git a/docs/assets/css/custom.css b/docs/assets/css/custom.css
new file mode 100644
index 0000000..e15ae2c
--- /dev/null
+++ b/docs/assets/css/custom.css
@@ -0,0 +1,24 @@
+@import url("https://fonts.googleapis.com/css2?family=Roboto:ital,wght@0,400;0,700;1,400&display=swap");
+
+:root {
+  --mono-hue: 222;
+  --mono-saturation: 14%;
+  --base-background-color: #282c35;
+  --theme-color: #66e0ff;
+  --link-color: var(--theme-color);
+
+  --base-font-family: Roboto, sans-serif;
+  --strong-font-weight: 700;
+
+  --search-flex-order: 0;
+  --search-margin: 1rem 0;
+  --docsify-example-panels-left-panel-width : 50%;
+  --docsify-example-panels-right-panel-width : 50%;
+}
+
+@media screen and (min-width: 1230px) {
+  :root {
+    --sidebar-width: 22rem;
+    --content-max-width : 66em;
+  }
+}
diff --git a/docs/favicon.ico b/docs/favicon.ico
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--- /dev/null
+++ b/docs/index.html
@@ -0,0 +1,72 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <title>My notebooks</title>
+    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
+    <meta name="description" content="Description" />
+    <meta
+      name="viewport"
+      content="width=device-width, initial-scale=1.0, minimum-scale=1.0"
+    />
+
+    <link rel="shortcut icon" href="favicon.ico" type="image/x-icon">
+    <link rel="icon" href="favicon.ico" type="image/x-icon">
+
+    <!-- Theme: Simple Dark -->
+    <link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify-themeable@0/dist/css/theme-simple-dark.css">
+    <!-- Katex stylesheets -->
+    <link rel="stylesheet" href="//cdn.jsdelivr.net/npm/katex@0.10.2/dist/katex.min.css">
+    <link rel="stylesheet" href="//cdn.jsdelivr.net/npm/katex-copytex@latest/dist/katex-copytex.min.css">
+
+    <link rel="stylesheet" href="assets/css/custom.css">
+  </head>
+  <body>
+    <div id="app">Loading content...</div>
+    <script>
+      window.$docsify = {
+        name: "DSA 2021 🏠",
+        repo: "https://github.com/stevengogogo/DataStructureAlgorithm",
+        basePath: "mdfiles",
+        relativePath: true,
+        externalLinkTarget: '_blank',
+
+        loadSidebar: true,
+        auto2top: true,
+        subMaxLevel: 3,
+
+        notFoundPage: true,
+        topMargin: 80,
+      };
+    </script>
+    <!-- Docsify v4 -->
+    <script src="//cdn.jsdelivr.net/npm/docsify@4/lib/docsify.min.js"></script>
+    <!-- docsify-themeable (latest v0.x.x) -->
+    <script src="//cdn.jsdelivr.net/npm/docsify-themeable@0/dist/js/docsify-themeable.min.js"></script>
+    <!--KaTeX -->
+    <script src="//cdn.jsdelivr.net/npm/docsify-katex@1/dist/docsify-katex.min.js"></script>
+    <script src="//cdn.jsdelivr.net/npm/katex-copytex@latest/dist/katex-copytex.min.js"></script>
+    <!-- Prismjs code highlighting -->
+    <script src="https://cdn.jsdelivr.net/npm/prismjs@1/components/prism-c.min.js"></script>
+    <script src="//cdn.jsdelivr.net/npm/prismjs@1/components/prism-julia.min.js"></script>
+    <script src="//cdn.jsdelivr.net/npm/prismjs@1/components/prism-bash.min.js"></script>
+    <script src="//cdn.jsdelivr.net/npm/prismjs@1/components/prism-python.min.js"></script>
+    <script src="//cdn.jsdelivr.net/npm/prismjs@1/components/prism-yaml.min.js"></script>
+    <!-- copy code Plugin -->
+    <script src="//cdn.jsdelivr.net/npm/docsify-copy-code@2/dist/docsify-copy-code.min.js"></script>
+    <!-- Search Box -->
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+
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+    <!-- Pangu -->
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+    <!-- docsify-example-panels (latest) -->
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+    <!-- Flexible alerts -->
+    <script src="//cdn.jsdelivr.net/npm/docsify-plugin-flexible-alerts@1/dist/docsify-plugin-flexible-alerts.min.js"></script>
+    
+  </body>
+</html>
diff --git a/docs/mdfiles/C.md b/docs/mdfiles/C.md
new file mode 100644
index 0000000..95824c5
--- /dev/null
+++ b/docs/mdfiles/C.md
@@ -0,0 +1,9 @@
+# Programming with C
+
+## Pointers
+
+
+## Function
+
+
+[cartpole](https://raw.githubusercontent.com/stevengogogo/GreatestCommonDivisor/main/src/main.c ':include')
\ No newline at end of file
diff --git a/docs/mdfiles/Lecture.md b/docs/mdfiles/Lecture.md
new file mode 100644
index 0000000..0d0980c
--- /dev/null
+++ b/docs/mdfiles/Lecture.md
@@ -0,0 +1,160 @@
+## Motivations of Data Structures and Algorithms
+
+
+<iframe width="700" height="400" src="https://www.youtube.com/embed/roRsiyDdMo0" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+
+### Debug
+
+![image](https://user-images.githubusercontent.com/29009898/110299183-581ccc80-8030-11eb-9f18-192f57d6922d.png)
+
+- integer `m` undefined
+- 會重複算到
+- `i<len`
+
+
+
+# Arrays and Linked Lists
+
+<iframe width="560" height="315" src="https://www.youtube.com/embed/by2jcmzeebs" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+---
+
+## 如何證明演算法正確?
+
+### Loop invariance
+
+After `i-th` iteration of the `for` loop, `arr[m]` is always the smallest among `arr[0]`,...., `arr[i]`
+- true when `i=0`
+- true when `i=k` → true when `i=k+1`
+
+#### 證明
+
+- 先寫要證明什麼
+- 看看離散數學的內容
+
+### Efficiency of Algorithm
+
+- Sequential search
+- Binary search
+
+### Pseudo code for `getMinIndex`
+
+#### Linear serach
+
+```c
+int getMinIndex(int arr[], int len){
+	int i;
+	int m=0;
+	for(i=0;i<len;i++){
+		if (arr[m] > arr[i]){
+			m=i;
+		}
+	}
+}
+
+```
+
+```c
+GET-MIN-INDEX(A)
+
+m = 1
+for i = 2 to A.length
+	if A[m] > A[i]
+		m = i
+
+return m
+
+```
+
+#### Selection sort
+
+![image](https://user-images.githubusercontent.com/29009898/110298600-b9906b80-802f-11eb-9d9e-55b1f2f927eb.png)
+
+
+### What is data structure?
+
+- Scheme of organizing data within computer
+- 快: 常常用的東西取的快
+- Good data structure needs proper maintenance algorithms:
+    - `Construct` / `Update` / `remove`
+
+### Why data structures and algorithms?
+
+- Data structures
+    - Storage
+    - Network, bandwidth
+- Algorithms
+    - Computation
+
+### Proper use: Tradeoff of different factors
+
+## C Programming  versus DSA
+
+- Test
+    - 怎麼測試程式碼
+    - 設計關鍵情形
+- Modualize
+    - 模組化
+- Tradeoff
+    - Theory
+    - Practice
+
+## What is Array?
+
+- Index
+- Memory is array
+- Address
+    - `arr[index]` , `memory[address]`
+- C programming
+    - Pointer
+
+### Array as memory block in C
+
+- Access: `arr[index]` → `memory[arr + index * sizeof(data)]`
+    - Array 可以快速 update 和拿出來
+- Maintenance: `malloc(sizeof(data)*length)`
+    - construct (length)
+
+![image](https://user-images.githubusercontent.com/29009898/110298769-ee9cbe00-802f-11eb-9461-cf2c5cac1088.png)
+       
+
+- Garbage collection
+
+## Orderred array
+
+![image](https://user-images.githubusercontent.com/29009898/110298847-0116f780-8030-11eb-8efe-de5e00896c29.png)
+
+### 可以試試 實做 orderred array
+
+- Insertion
+- remove
+
+## Sorting
+
+### Insertion Sort
+
+$O(n^2)$ 
+
+![](https://user-images.githubusercontent.com/29009898/110297582-a335e000-802e-11eb-94dd-322eb7caccb2.png)
+
+### Selection Sort
+
+$O(n^2)$ 
+
+![Untitled 1](https://user-images.githubusercontent.com/29009898/110297584-a3ce7680-802e-11eb-8400-65c32a2ae1ca.png)
+
+## Sequential search algorithm
+
+---
+
+## 作業0
+
+![Untitled](https://user-images.githubusercontent.com/29009898/110297587-a4670d00-802e-11eb-9c69-6fe3de90e824.png)
+
+- 會走到沒有 define 的地區
+- 執行錯誤
+- `ary[-4]`
+- `segmentation fault` 每次呼叫都是系統給空間，如果取用非法空間就是 `segmentation fault`
+
+
diff --git a/docs/mdfiles/README.md b/docs/mdfiles/README.md
new file mode 100644
index 0000000..b34dbb3
--- /dev/null
+++ b/docs/mdfiles/README.md
@@ -0,0 +1,7 @@
+# Data Structure and Algorithm 
+
+## Course Website
+https://cool.ntu.edu.tw/courses/4621
+
+## DSA Judge
+https://dsa-2021.csie.org/#!/
diff --git a/docs/mdfiles/_sidebar.md b/docs/mdfiles/_sidebar.md
new file mode 100644
index 0000000..6145f67
--- /dev/null
+++ b/docs/mdfiles/_sidebar.md
@@ -0,0 +1,5 @@
+- [🏠 **Home**](README.md)
+- [🤹 **Lecture Note**](lec/)
+- [📒 **Assignments**](assignment.md)
+- [🤖️ **C Programming**](C.md)
+- [**Markdown**](how-to-use-docify.md)
\ No newline at end of file
diff --git a/docs/mdfiles/assignment.md b/docs/mdfiles/assignment.md
new file mode 100644
index 0000000..01197a4
--- /dev/null
+++ b/docs/mdfiles/assignment.md
@@ -0,0 +1,8 @@
+# Assignment
+
+## Homework 0
+
+
+|Porblem|Status|
+|---|---|
+|rgrg|grg|
\ No newline at end of file
diff --git a/docs/mdfiles/how-to-use-docify.md b/docs/mdfiles/how-to-use-docify.md
new file mode 100644
index 0000000..6a6d3f2
--- /dev/null
+++ b/docs/mdfiles/how-to-use-docify.md
@@ -0,0 +1,633 @@
+# Markdown syntax
+
+Sourced from [Docsify themable](https://jhildenbiddle.github.io/docsify-themeable/).
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Headings
+
+<!-- div:left-panel -->
+
+# Heading 1 {docsify-ignore}
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse luctus
+nulla eu ex varius, a varius elit tincidunt. Aenean arcu magna, gravida id purus
+a, interdum convallis turpis. Aenean id ipsum eu tortor sollicitudin scelerisque
+in quis elit.
+
+## Heading 2 {docsify-ignore}
+
+Vestibulum lobortis laoreet nunc vel vulputate. In et augue non lectus
+pellentesque molestie et ac justo. Sed sed turpis ut diam gravida sagittis nec
+at neque. Vivamus id tellus est. Nam ac dignissim mi. Vestibulum nec sem
+convallis, condimentum augue at, commodo diam.
+
+### Heading 3 {docsify-ignore}
+
+Suspendisse sit amet tincidunt nibh, ac interdum velit. Ut orci diam, dignissim
+at enim sit amet, placerat rutrum magna. Mauris consectetur nibh eget sem
+feugiat, sit amet congue quam laoreet. Curabitur sed massa metus.
+
+#### Heading 4 {docsify-ignore}
+
+Donec odio orci, facilisis ac vehicula in, vestibulum ut urna. Ut bibendum
+ullamcorper risus, ac euismod leo maximus sed. In pulvinar sagittis rutrum.
+Morbi quis cursus diam. Cras ac laoreet nulla, rhoncus sodales dui.
+
+##### Heading 5 {docsify-ignore}
+
+Commodo sit veniam nulla cillum labore ullamco aliquip quis. Consequat nulla
+fugiat consequat ex duis proident. Adipisicing excepteur tempor exercitation ad.
+Consectetur voluptate Lorem sint elit exercitation ullamco dolor.
+
+###### Heading 6 {docsify-ignore}
+
+Ipsum ea amet dolore mollit incididunt fugiat nulla laboris est sint voluptate.
+Ex culpa id amet ipsum amet pariatur ipsum officia sit laborum irure ullamco
+deserunt. Consequat qui tempor occaecat nostrud proident.
+
+<!-- div:right-panel -->
+
+```markdown
+# Heading 1
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse luctus
+nulla eu ex varius, a varius elit tincidunt. Aenean arcu magna, gravida id purus
+a, interdum convallis turpis. Aenean id ipsum eu tortor sollicitudin scelerisque
+in quis elit.
+
+## Heading 2
+
+Vestibulum lobortis laoreet nunc vel vulputate. In et augue non lectus
+pellentesque molestie et ac justo. Sed sed turpis ut diam gravida sagittis nec
+at neque. Vivamus id tellus est. Nam ac dignissim mi. Vestibulum nec sem
+convallis, condimentum augue at, commodo diam.
+
+### Heading 3
+
+Suspendisse sit amet tincidunt nibh, ac interdum velit. Ut orci diam, dignissim
+at enim sit amet, placerat rutrum magna. Mauris consectetur nibh eget sem
+feugiat, sit amet congue quam laoreet. Curabitur sed massa metus.
+
+#### Heading 4
+
+Donec odio orci, facilisis ac vehicula in, vestibulum ut urna. Ut bibendum
+ullamcorper risus, ac euismod leo maximus sed. In pulvinar sagittis rutrum.
+Morbi quis cursus diam. Cras ac laoreet nulla, rhoncus sodales dui.
+
+##### Heading 5
+
+Commodo sit veniam nulla cillum labore ullamco aliquip quis. Consequat nulla
+fugiat consequat ex duis proident. Adipisicing excepteur tempor exercitation ad.
+Consectetur voluptate Lorem sint elit exercitation ullamco dolor.
+
+###### Heading 6
+
+Ipsum ea amet dolore mollit incididunt fugiat nulla laboris est sint voluptate.
+Ex culpa id amet ipsum amet pariatur ipsum officia sit laborum irure ullamco
+deserunt. Consequat qui tempor occaecat nostrud proident.
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Text
+
+<!-- div:left-panel -->
+
+Body text
+
+**Bold text**
+
+*Italic text*
+
+~~Strikethrough~~
+
+<mark>Marked text</mark>
+
+<pre>Preformatted text</pre>
+
+<small>Small Text</small>
+
+This is <sub>subscript</sub>
+
+This is <sup>superscript</sup>
+
+<abbr title="World Health Organization">WHO</abbr>
+
+
+<!-- div:right-panel -->
+
+```markdown
+Body text
+
+**Bold text**
+
+*Italic text*
+
+~~Strikethrough~~
+
+<mark>Marked text</mark>
+
+<pre>Preformatted text</pre>
+
+<small>Small Text</small>
+
+This is <sub>subscript</sub>
+
+This is <sup>superscript</sup>
+
+<abbr title="World Health Organization">WHO</abbr>
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Links
+
+<!-- div:left-panel -->
+
+[Inline link](https://google.com)
+
+[Inline link with title](https://google.com "Google")
+
+[Reference link by name][link1]
+
+[Reference link by number][1]
+
+[Reference link by self]
+
+[link1]: https://google.com
+[1]: https://google.com
+[Reference link by self]: https://google.com
+
+<!-- div:right-panel -->
+
+```markdown
+[Inline link](https://google.com)
+
+[Inline link with title](https://google.com "Google")
+
+[Reference link by name][link1]
+
+[Reference link by number][1]
+
+[Reference link by self]
+
+[link1]: https://google.com
+[1]: https://google.com
+[Reference link by self]: https://google.com
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Lists
+
+<!-- div:left-panel -->
+
+**Ordered Lists**
+
+1. Ordered 1
+1. Ordered 2
+   1. Ordered 2a
+   1. Ordered 2b
+   1. Ordered 2c
+1. Ordered 3
+
+**Unordered Lists**
+
+- Unordered 1
+- Unordered 2
+  - Unordered 2a
+  - Unordered 2b
+  - Unordered 2c
+- Unordered 3
+
+**Task Lists**
+
+- [x] Task 1
+- [ ] Task 2
+  - [x] Subtask A
+  - [ ] Subtask B
+- [ ] Task 3
+
+<!-- div:right-panel -->
+
+```markdown
+**Ordered Lists**
+
+1. Ordered 1
+1. Ordered 2
+   1. Ordered 2a
+   1. Ordered 2b
+   1. Ordered 2c
+1. Ordered 3
+
+**Unordered Lists**
+
+- Unordered 1
+- Unordered 2
+  - Unordered 2a
+  - Unordered 2b
+  - Unordered 2c
+- Unordered 3
+
+**Task Lists**
+
+- [x] Task 1
+- [ ] Task 2
+  - [x] Subtask A
+  - [ ] Subtask B
+- [ ] Task 3
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Blockquotes
+
+<!-- div:left-panel -->
+
+> Cras aliquet nulla quis metus tincidunt, sed placerat enim cursus. Etiam
+> turpis nisl, posuere eu condimentum ut, interdum a risus. Sed non luctus mi.
+> Quisque malesuada risus sit amet tortor aliquet, a posuere ex iaculis. Vivamus
+> ultrices enim dui, eleifend porttitor elit aliquet sed.
+>
+> *- Quote Source*
+
+<!-- div:right-panel -->
+
+```markdown
+> Cras aliquet nulla quis metus tincidunt, sed placerat enim cursus. Etiam
+> turpis nisl, posuere eu condimentum ut, interdum a risus. Sed non luctus mi.
+> Quisque malesuada risus sit amet tortor aliquet, a posuere ex iaculis. Vivamus
+> ultrices enim dui, eleifend porttitor elit aliquet sed.
+>
+> *- Quote Source*
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Code
+
+<!-- div:left-panel -->
+
+This is `inline code`
+
+```javascript
+const add   = (num1, num2) => num1 + num2;
+const total = add(1, 2);
+
+console.log(total); // 3
+```
+
+```html
+<body>
+    <p>Hello</p>
+</body>
+```
+
+<!-- div:right-panel -->
+
+````markdown
+This is `inline code`
+
+```javascript
+const add   = (num1, num2) => num1 + num2;
+const total = add(1, 2);
+
+console.log(total); // 3
+```
+
+```html
+<body>
+    <p>Hello</p>
+</body>
+```
+````
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Notices
+
+Note, tip, warning, and attention notices are provided by [Flexible alerts](https://github.com/fzankl/docsify-plugin-flexible-alerts)
+
+<!-- div:left-panel -->
+
+!> **Important** notice with `inline code` and additional placeholder text used
+to force the content to wrap and span multiple lines.
+
+?> **Tip** notice with `inline code` and additional placeholder text used to
+force the content to wrap and span multiple lines.
+
+> [!NOTE]
+> An alert of type 'note' using global style 'callout'.
+
+> [!TIP]
+> An alert of type 'tip' using global style 'callout'.
+
+> [!WARNING]
+> An alert of type 'warning' using global style 'callout'.
+
+> [!ATTENTION]
+> An alert of type 'attention' using global style 'callout'.
+
+<!-- div:right-panel -->
+
+```markdown
+!> **Important** notice with `inline code` and additional placeholder text used
+to force the content to wrap and span multiple lines.
+
+?> **Tip** notice with `inline code` and additional placeholder text used to
+force the content to wrap and span multiple lines.
+
+> [!NOTE]
+> An alert of type 'note' using global style 'callout'.
+
+> [!TIP]
+> An alert of type 'tip' using global style 'callout'.
+
+> [!WARNING]
+> An alert of type 'warning' using global style 'callout'.
+
+> [!ATTENTION]
+> An alert of type 'attention' using global style 'callout'.
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Tabs
+
+Provided by [docsify-tabs](https://jhildenbiddle.github.io/docsify-tabs).
+
+<!-- div:left-panel -->
+
+<!-- tabs:start -->
+
+#### **English**
+
+Hello!
+
+#### **French**
+
+Bonjour!
+
+#### **Italian**
+
+Ciao!
+
+<!-- tabs:end -->
+
+<!-- div:right-panel -->
+
+```markdown
+<!-- tabs:start -->
+
+#### **English**
+
+Hello!
+
+#### **French**
+
+Bonjour!
+
+#### **Italian**
+
+Ciao!
+
+<!-- tabs:end -->
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Tables
+
+Checkout [Markdown table generator](https://www.tablesgenerator.com/markdown_tables) to create tables in Markdown.
+
+<!-- div:left-panel -->
+
+| Left Align | Center Align | Right Align | Non-Breaking Header |
+| ---------- |:------------:| -----------:| ------------------------------ |
+| A1         | A2           | A3          | A4                             |
+| B1         | B2           | B3          | B4                             |
+| C1         | C2           | C3          | C4                             |
+
+<!-- div:right-panel -->
+
+```markdown
+| Left Align | Center Align | Right Align | Non-Breaking Header |
+| ---------- |:------------:| -----------:| ------------------------------ |
+| A1         | A2           | A3          | A4                             |
+| B1         | B2           | B3          | B4                             |
+| C1         | C2           | C3          | C4                             |
+```
+
+<!-- panels:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Keyboard
+
+Using HTML `<kbd>key</kbd>`.
+
+<!-- div:left-panel -->
+
+<kbd>&uarr;</kbd> Arrow Up
+
+<kbd>&darr;</kbd> Arrow Down
+
+<kbd>&larr;</kbd> Arrow Left
+
+<kbd>&rarr;</kbd> Arrow Right
+
+<kbd>&#8682;</kbd> Caps Lock
+
+<kbd>&#8984;</kbd> Command
+
+<kbd>&#8963;</kbd> Control
+
+<kbd>&#9003;</kbd> Delete
+
+<kbd>&#8998;</kbd> Delete (Forward)
+
+<kbd>&#8600;</kbd> End
+
+<kbd>&#8996;</kbd> Enter
+
+<kbd>&#9099;</kbd> Escape
+
+<kbd>&#8598;</kbd> Home
+
+<kbd>&#8670;</kbd> Page Up
+
+<kbd>&#8671;</kbd> Page Down
+
+<kbd>&#8997;</kbd> Option, Alt
+
+<kbd>&#8629;</kbd> Return
+
+<kbd>&#8679;</kbd> Shift
+
+<kbd>&#9251;</kbd> Space
+
+<kbd>&#8677;</kbd> Tab
+
+<kbd>&#8676;</kbd> Tab + Shift
+
+<!-- div:right-panel -->
+
+```markdown
+<kbd>&uarr;</kbd> Arrow Up
+
+<kbd>&darr;</kbd> Arrow Down
+
+<kbd>&larr;</kbd> Arrow Left
+
+<kbd>&rarr;</kbd> Arrow Right
+
+<kbd>&#8682;</kbd> Caps Lock
+
+<kbd>&#8984;</kbd> Command
+
+<kbd>&#8963;</kbd> Control
+
+<kbd>&#9003;</kbd> Delete
+
+<kbd>&#8998;</kbd> Delete (Forward)
+
+<kbd>&#8600;</kbd> End
+
+<kbd>&#8996;</kbd> Enter
+
+<kbd>&#9099;</kbd> Escape
+
+<kbd>&#8598;</kbd> Home
+
+<kbd>&#8670;</kbd> Page Up
+
+<kbd>&#8671;</kbd> Page Down
+
+<kbd>&#8997;</kbd> Option, Alt
+
+<kbd>&#8629;</kbd> Return
+
+<kbd>&#8679;</kbd> Shift
+
+<kbd>&#9251;</kbd> Space
+
+<kbd>&#8677;</kbd> Tab
+
+<kbd>&#8676;</kbd> Tab + Shift
+```
+
+<!-- panels:end -->
+
+
+## Horizontal Rule
+
+<!-- tabs:start -->
+
+#### ** Rendered **
+
+---
+
+#### ** Markdown **
+
+```markdown
+---
+```
+
+<!-- tabs:end -->
+
+<!-- panels:start -->
+<!-- div:title-panel -->
+
+## Images
+
+<!-- div:left-panel -->
+
+Inline-style
+
+![alt text](//source.unsplash.com/daily "Provided by unsplash.com")
+
+Reference-style
+
+![alt text][logo]
+
+[logo]: //source.unsplash.com/collection/881815 "Provided by unsplash.com"
+
+<!-- div:right-panel -->
+
+```markdown
+**Inline**
+
+![alt text](//source.unsplash.com/daily "Provided by unsplash.com")
+
+**Reference**
+
+![alt text][logo]
+
+[logo]: //source.unsplash.com/collection/881815 "Provided by unsplash.com"
+```
+
+<!-- panels:end -->
+
+## Emoji
+
+A complete list is available here: [Emoji Cheat Sheet](https://www.webpagefx.com/tools/emoji-cheat-sheet/). I personally just copy-paste from [Emojipedia](https://emojipedia.org).
+
+## Include
+
+Format to include other files:
+
+```markdown
+[LABLE](url ':include')
+
+[LABLE](url ':include :type=code')
+```
+
+### Gist (or files outside)
+
+```markdown
+[cartpole](https://gist.githubusercontent.com/sosiristseng/b57eb8c05b2b9126d48e763206a1667a/raw/cartpole.py ':include')
+```
+
+[cartpole](https://gist.githubusercontent.com/sosiristseng/b57eb8c05b2b9126d48e763206a1667a/raw/cartpole.py ':include')
+
+
+### Files inside
+
+```markdown
+[GitlabCI](_media/gitlab-ci.yaml ':include')
+```
+
+```markdown
+[example](_media/example.md ':include')
+```
+
+```markdown
+[bird](../_media/birb.mp4 ':include :type=video autoplay loop muted playsinline')
+```
diff --git a/docs/mdfiles/lec/00_Introduction.md b/docs/mdfiles/lec/00_Introduction.md
new file mode 100644
index 0000000..5535ad7
--- /dev/null
+++ b/docs/mdfiles/lec/00_Introduction.md
@@ -0,0 +1,14 @@
+# Motivations of Data Structures and Algorithms
+
+
+<iframe width="700" height="400" src="https://www.youtube.com/embed/roRsiyDdMo0" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+
+## Debug
+
+![image](https://user-images.githubusercontent.com/29009898/110299183-581ccc80-8030-11eb-9f18-192f57d6922d.png)
+
+- integer `m` undefined
+- 會重複算到
+- `i<len`
+
diff --git a/docs/mdfiles/lec/01_linked_list.md b/docs/mdfiles/lec/01_linked_list.md
new file mode 100644
index 0000000..633c505
--- /dev/null
+++ b/docs/mdfiles/lec/01_linked_list.md
@@ -0,0 +1,142 @@
+# Arrays and Linked Lists
+
+<iframe width="560" height="315" src="https://www.youtube.com/embed/by2jcmzeebs" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+---
+
+# 如何證明演算法正確?
+
+## Loop invariance
+
+After `i-th` iteration of the `for` loop, `arr[m]` is always the smallest among `arr[0]`,...., `arr[i]`
+- true when `i=0`
+- true when `i=k` → true when `i=k+1`
+
+### 證明
+
+- 先寫要證明什麼
+- 看看離散數學的內容
+
+## Efficiency of Algorithm
+
+- Sequential search
+- Binary search
+
+## Pseudo code for `getMinIndex`
+
+### Linear serach
+
+```c
+int getMinIndex(int arr[], int len){
+	int i;
+	int m=0;
+	for(i=0;i<len;i++){
+		if (arr[m] > arr[i]){
+			m=i;
+		}
+	}
+}
+
+```
+
+```c
+GET-MIN-INDEX(A)
+
+m = 1
+for i = 2 to A.length
+	if A[m] > A[i]
+		m = i
+
+return m
+
+```
+
+### Selection sort
+
+![image](https://user-images.githubusercontent.com/29009898/110298600-b9906b80-802f-11eb-9d9e-55b1f2f927eb.png)
+
+
+## What is data structure?
+
+- Scheme of organizing data within computer
+- 快: 常常用的東西取的快
+- Good data structure needs proper maintenance algorithms:
+    - `Construct` / `Update` / `remove`
+
+## Why data structures and algorithms?
+
+- Data structures
+    - Storage
+    - Network, bandwidth
+- Algorithms
+    - Computation
+
+## Proper use: Tradeoff of different factors
+
+# C Programming  versus DSA
+
+- Test
+    - 怎麼測試程式碼
+    - 設計關鍵情形
+- Modualize
+    - 模組化
+- Tradeoff
+    - Theory
+    - Practice
+
+# What is Array?
+
+- Index
+- Memory is array
+- Address
+    - `arr[index]` , `memory[address]`
+- C programming
+    - Pointer
+
+## Array as memory block in C
+
+- Access: `arr[index]` → `memory[arr + index * sizeof(data)]`
+    - Array 可以快速 update 和拿出來
+- Maintenance: `malloc(sizeof(data)*length)`
+    - construct (length)
+
+![image](https://user-images.githubusercontent.com/29009898/110298769-ee9cbe00-802f-11eb-9461-cf2c5cac1088.png)
+       
+
+- Garbage collection
+
+# Orderred array
+
+![image](https://user-images.githubusercontent.com/29009898/110298847-0116f780-8030-11eb-8efe-de5e00896c29.png)
+
+## 可以試試 實做 orderred array
+
+- Insertion
+- remove
+
+# Sorting
+
+## Insertion Sort
+
+$O(n^2)$ 
+
+![](https://user-images.githubusercontent.com/29009898/110297582-a335e000-802e-11eb-94dd-322eb7caccb2.png)
+
+## Selection Sort
+
+$O(n^2)$ 
+
+![Untitled 1](https://user-images.githubusercontent.com/29009898/110297584-a3ce7680-802e-11eb-8400-65c32a2ae1ca.png)
+
+# Sequential search algorithm
+
+---
+
+# 作業0
+
+![Untitled](https://user-images.githubusercontent.com/29009898/110297587-a4670d00-802e-11eb-9c69-6fe3de90e824.png)
+
+- 會走到沒有 define 的地區
+- 執行錯誤
+- `ary[-4]`
+- `segmentation fault` 每次呼叫都是系統給空間，如果取用非法空間就是 `segmentation fault`
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+# Julia tutorial
+
+1. [Think Julia](https://benlauwens.github.io/ThinkJulia.jl/latest/book.html)
+2. [From zero to Julia](https://techytok.com/from-zero-to-julia/)
+3. [Julia cheat sheet](https://juliadocs.github.io/Julia-Cheat-Sheet/) if you are familiar with Python and/or MATLAB.
+4. [Official Julia Manual](https://docs.julialang.org/) for the API.
+5. [Julia for Pythonistas](https://colab.research.google.com/github/ageron/julia_notebooks/blob/master/Julia_for_Pythonistas.ipynb)
+6. [Learn Julia](https://julialang.org/learning/) from the official website.
+
+# Why Julia?
+
+[John F. Gibson's talk](https://github.com/johnfgibson/whyjulia/blob/master/1-whyjulia.ipynb)
+
+- Python/MATLAB-like syntax + natural math presentation
+- C-like speed (!) + built-in parallelism
+- Composable and extensible (e.g. DiffEq + ANN)
+- Right tool for this course to solve differential equations and stochastic simulations
+
+## Why not Julia?
+
+- Time to first plot (TTFF). Code needs to be compiled first so it feels less responsive than Python. [Somebody just gave up](https://www.zverovich.net/2016/05/13/giving-up-on-julia.html).
+- Less libraries in some domains. (e.g. metabolic networks)
+- [Arrays start at one](https://i.imgur.com/VRSkSGd.jpg)
+
+# Install and run Julia
+
+[Download Julia](https://julialang.org/downloads/) and install. You could give version `1.6-rc1` a try because it loads much fater than previous versions.
+
+## REPL workflow
+
+Run the julia REPL (terminal) and start typing.
+
+## Jupyter workflow
+
+This workflow suits demonstration
+
+Open the Julia terminal and enter the following commands to install IJulia, the Julia kernel for Jupyter notebooks.
+
+```julia
+using Pkg
+
+pkg"add IJulia"
+```
+
+And then run Jupyter Lab either from the Julia terminal.
+
+```julia
+using IJulia
+
+# It will prompt you to install jupyter lab, enter y to proceed
+# Will open at ${HOME}, thatby default it is "C:\Users\yourname\" in Windows systems.
+IJulia.jupyterlab()
+```
+
+Or from Anaconda's Jupyter lab interface if you have installed Anaconda.
+
+## VS Code workflow
+
+[VS Code](https://code.visualstudio.com/) with [Julia extension](https://www.julia-vscode.org/) works better for structured code. See this [Youtube video](https://www.youtube.com/watch?v=IdhnP00Y1Ks).
+
+!> Juno, the original IDE for Julia, is [in maintenance mode](https://www.youtube.com/watch?v=rQ7D1lXt3GM).
+
+## My computer cannot run Julia
+
+### Google collab
+
+Open this [Julia for Pythonistas](https://colab.research.google.com/github/ageron/julia_notebooks/blob/master/Julia_for_Pythonistas.ipynb) notebook, save a copy to your Google drive, and run it.
+
+### Nextjournal
+
+[Nextjournal](https://nextjournal.com/) provides a notebook-like UI for reproducible research.
+
+You could use [Tmy template for Julia 1.6 + Differential Equations](https://nextjournal.com/bebi5009/julia-template). 
diff --git a/docs/mdfiles/lec/_sidebar.md b/docs/mdfiles/lec/_sidebar.md
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+- [🤹 **Lecture Note**](README.md)
+- [Introduction](00_Introduction.md)
+- [Arrays and Linked Lists](01_linked_list.md)
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