<font color="#8A2BE2">[DS筆記]</font> Linked List 鏈結串列
===

範例零 比較不好的寫法
---
<br>

class Node{
  constructor(val) {
      this.val = val;
      this.next = null;
  }
}

var first = new Node("Hi")
first.next = new Node("there")
first.next.next = new Node("how")
first.next.next.next = new Node("are")
first.next.next.next.next = new Node("you")

console.log(first)

[replit連結：](https://replit.com/@bobyin22/Chuan-Tong#index.js)
<br>

範例一 push
---
### 單獨push程式碼

push(val){                          //push(傳入參數)
      var newNode = new Node(val)   //複製一份Node類 給newNode變數  
      if(!this.head) {              //如果 頭     空
          this.head = newNode;      //    頭 當 newNode變數
          this.tail = this.head;    //    尾 當 newNode變數
      } else {                      //如果 頭   非空
          this.tail.next = newNode; //    尾 當 newNode變數
          this.tail = newNode       //    尾 當 newNode變數
      }
      this.length++                 //長度+1
      return this;
  }

### push影片
{%youtube lt8dnCZE918 %}
### 完整push程式碼

class Node {
  constructor(val) {    //只有一個參數
      this.val = val;   //把參數 給目前值
      this.next = null; //指向   空
  }
}

class SinglyLinkedList {
  constructor() {
      this.head = null;  //頭 空
      this.tail = null;  //尾 空
      this.length = 0;   //長 0
  }
  push(val){             //push(傳入參數)
      var newNode = new Node(val)    //複製一份Node類 給newNode變數
      if(!this.head) {               //如果 頭     空
          this.head = newNode;       //    頭 當 newNode變數
          this.tail = this.head;     //    尾 當 newNode變數
      } else {                       //如果 頭   非空
          this.tail.next = newNode;  //    尾 當 newNode變數
          this.tail = newNode        //    尾 當 newNode變數
      }
      this.length++                  //長度+1
      return this;
  }
}

var list =  new SinglyLinkedList()   //複製一份SinglyLinkedList類 給list變數
console.log(list)

list.push("HELLO")
list.push("GOODBYE")
list.push("99")

console.log(list)

[replit連結：](https://replit.com/@bobyin22/linked-list-push#index.js)
<br>

範例二 pop 刪除尾
---
### 單獨pop程式碼

  pop() {
      if(!this.head) return undefined; //沒有值，不做pop動作
      var current = this.head;         //頭          當 current變數
      var newTail = current;           //current變數 當 newTail變數
      while(current.next){             //當 current變數.next 還有值
          newTail = current;           //    頭 等於 尾
          current = current.next;      //    頭 等於 尾
      }
      this.tail = newTail;             
      this.tail.next = null;            //尾.next 等於空
      this.length--;
      if(this.length === 0) {           //沒有值
          this.head = null;             //頭 空
          this.tail = null;             //尾 空
      }
      return current;
  }

### pop影片
{%youtube ILHaaUV6SJ8%}
### 完整pop程式碼

class Node {
  constructor(val) {
      this.val = val;
      this.next = null;
  }
}

class SinglyLinkedList {
  constructor() {
      this.head = null;
      this.tail = null;
      this.length = 0;
  }
  push(val){
      var newNode = new Node(val)
      if(!this.head) {  
          this.head = newNode; 
          this.tail = this.head; 
      } else {
          this.tail.next = newNode;
          this.tail = newNode
      }
      this.length++
      return this;
  }
  pop() {
      if(!this.head) return undefined;
      var current = this.head;
      var newTail = current;
      while(current.next){
          newTail = current;
          current = current.next;
      }
      this.tail = newTail;
      this.tail.next = null;
      this.length--;
      if(this.length === 0) {
          this.head = null;
          this.tail = null;
      }
      return current;
  }
}

var list =  new SinglyLinkedList()
//console.log(list)

list.push("HELLO")
list.push("GOODBYE")
list.push("99")
console.log(list)

list.pop()
console.log(list)

<br>

範例三 shift 刪除頭
---
### 單獨shift程式碼

shift() {
    if(!this.head) return undefined;
    var currentHead = this.head
    this.head = currentHead.next
    this.length--;
    if(this.length === 0) {
          this.tail = null;
      }
    return currentHead
    console.log(this)

  }

### shift影片
{%youtube PjT0dYf087w %}
### 完整shift程式碼

class Node {
  constructor(val) {
      this.val = val;
      this.next = null;
  }
}

class SinglyLinkedList {
  constructor() {
      this.head = null;
      this.tail = null;
      this.length = 0;
  }
  push(val){
      var newNode = new Node(val)
      if(!this.head) {  //如果沒有值
          this.head = newNode; //複製一個Node類 當作 SinglyLinkedList類的head
          this.tail = this.head; 
      } else {
          this.tail.next = newNode;
          this.tail = newNode
      }
      this.length++
      return this;
  }
  pop() {
      if(!this.head) return undefined; //沒有值，不做pop動作
      var current = this.head;
      var newTail = current;
      while(current.next){
          newTail = current;
          current = current.next;
      }
      this.tail = newTail;
      this.tail.next = null;
      this.length--;
      if(this.length === 0) {
          this.head = null;
          this.tail = null;
      }
      return current;
  }
  shift() {
    if(!this.head) return undefined;
    var currentHead = this.head
    this.head = currentHead.next
    this.length--;
    if(this.length === 0) {
          this.tail = null;
      }
    return currentHead
    console.log(this)

  }
}

var list =  new SinglyLinkedList()
//console.log(list)

list.push("HELLO")
list.push("GOODBYE")
list.push("99")
console.log(list)  //HELLO->GOODBYE->99

list.pop()
console.log(list)  //HELLO->GOODBYE

list.shift()
console.log(list)  //GOODBYE

list.shift()
console.log(list)  //null

<br>

範例四 unshift 加入頭
---
### 單獨 unshift程式碼

### unshift影片
{%youtube K1hBCHCZC1s %}

### 完整 unshift程式碼

<br>

###### tags: `[DS]`