feat: linked-list add length property (#8)

* feat: linked-list add length property

* perf: expose length property

* fix: length getter should be public

Author: hifizz

src/linked-list/__tests__/index.ts

@@ -14,22 +14,14 @@ describe('LinkedList class', () => {
     expect(linkedList).toBeInstanceOf(Object)
     expect(linkedList.head).toBe(null)
     expect(linkedList.tail).toBe(null)
+    expect(linkedList.length).toBe(0)
   })
 
   describe('Method append()', () => {
-    it('should be a chain method', () => {
-      linkedList
-        .append(1)
-        .append(2)
-        .append(3)
-      expect(linkedList.head).toBeDefined()
-      expect(linkedList.tail).toBeDefined()
-      expect((linkedList.head as Node).value).toBe(1)
-      expect((linkedList.tail as Node).value).toBe(3)
-    })
-
     it('should append a node to linkedlist', () => {
+      expect(linkedList.length).toBe(0)
       linkedList.append(1)
+      expect(linkedList.length).toBe(1)
 
       expect(linkedList.head).toBeDefined()
       expect(linkedList.head).toBeInstanceOf(Node)
@@ -44,6 +36,18 @@ describe('LinkedList class', () => {
       expect(linkedList.head).toBe(linkedList.tail)
     })
 
+    it('should be a chain method', () => {
+      linkedList
+        .append(1)
+        .append(2)
+        .append(3)
+      expect(linkedList.head).toBeDefined()
+      expect(linkedList.tail).toBeDefined()
+      expect((linkedList.head as Node).value).toBe(1)
+      expect((linkedList.tail as Node).value).toBe(3)
+      expect(linkedList.length).toBe(3)
+    })
+
     it('should append 2 values be linked', () => {
       linkedList.append(1).append(2)
 
@@ -90,6 +94,7 @@ describe('LinkedList class', () => {
       linkedList.prepend(2)
 
       expect(linkedList.toString()).toBe('2,1')
+      expect(linkedList.length).toBe(2)
     })
 
     it('should handle head & tail correctly', () => {
@@ -102,6 +107,7 @@ describe('LinkedList class', () => {
       expect(linkedList.toString()).toBe('1,2,3,4,5')
       expect((linkedList.head as Node).value).toBe(1)
       expect((linkedList.tail as Node).value).toBe(5)
+      expect(linkedList.length).toBe(5)
     })
   })
 
@@ -152,6 +158,7 @@ describe('LinkedList class', () => {
 
     it('should return null if the list is empty()', () => {
       expect(linkedList.delete(1)).toBe(null)
+      expect(linkedList.length).toBe(0)
     })
 
     it('should delete nothing if not found value', () => {
@@ -162,6 +169,7 @@ describe('LinkedList class', () => {
 
       const deletedNode = linkedList.delete(6)
       expect(deletedNode).toBe(null)
+      expect(linkedList.length).toBe(3)
       expect((linkedList.head as Node).value).toBe(1)
       expect(((linkedList.head as Node).next as Node).value).toBe(2)
       expect((linkedList.tail as Node).value).toBe(3)
@@ -176,6 +184,7 @@ describe('LinkedList class', () => {
 
       const deletedNode = linkedList.delete(3)
       expect((deletedNode as Node).value).toBe(3)
+      expect(linkedList.length).toBe(2)
       expect((linkedList.head as Node).value).toBe(1)
       expect(((linkedList.head as Node).next as Node).value).toBe(2)
       expect((linkedList.tail as Node).value).toBe(2)
@@ -184,6 +193,7 @@ describe('LinkedList class', () => {
       linkedList.append(3)
 
       const deletedNode2 = linkedList.delete(1)
+      expect(linkedList.length).toBe(2)
       expect((deletedNode2 as Node).value).toBe(1)
       expect((linkedList.head as Node).value).toBe(2)
       expect((linkedList.tail as Node).value).toBe(3)
@@ -194,6 +204,7 @@ describe('LinkedList class', () => {
 
       expect(linkedList.head).toBe(null)
       expect(linkedList.tail).toBe(null)
+      expect(linkedList.length).toBe(0)
     })
   })
 
@@ -207,7 +218,7 @@ describe('LinkedList class', () => {
         .append(5)
       expect((linkedList.deleteHead() as Node).value).toBe(1)
       expect(linkedList.toString()).toBe('2,3,4,5')
-
+      expect(linkedList.length).toBe(4)
       expect((linkedList.head as Node).value).toBe(2)
       expect((linkedList.tail as Node).value).toBe(5)
     })
@@ -228,6 +239,7 @@ describe('LinkedList class', () => {
     it('should delete tail node and handle head & tail correctly', () => {
       linkedList.append(1).deleteTail()
       expect(linkedList.toString()).toBe('')
+      expect(linkedList.length).toBe(0)
       expect(linkedList.head).toBe(null)
       expect(linkedList.tail).toBe(null)
 
@@ -238,16 +250,15 @@ describe('LinkedList class', () => {
         .append(4)
         .append(5)
       linkedList.deleteTail()
+      expect(linkedList.length).toBe(4)
       expect(linkedList.toString()).toBe('1,2,3,4')
       expect((linkedList.head as Node).value).toBe(1)
       expect((linkedList.tail as Node).value).toBe(4)
     })
 
     it('should return null when list is empty', () => {
       expect(linkedList.deleteTail()).toBe(null)
-      linkedList.append(1)
-      linkedList.append(2)
-      expect((linkedList.deleteHead() as Node).value).toBe(1)
+      expect(linkedList.length).toBe(0)
     })
   })
 
@@ -279,6 +290,7 @@ describe('LinkedList class', () => {
       linkedList.insert(5, 1)
 
       expect(linkedList.toString()).toBe('1,5,2,1,3')
+      expect(linkedList.length).toBe(5)
       expect((linkedList.head as Node).value).toBe(1)
       expect((linkedList.tail as Node).value).toBe(3)
     })
@@ -291,6 +303,7 @@ describe('LinkedList class', () => {
         .append(3)
       linkedList.insert(5, 3)
 
+      expect(linkedList.length).toBe(5)
       expect(linkedList.toString()).toBe('1,2,1,3,5')
       expect((linkedList.head as Node).value).toBe(1)
       expect((linkedList.tail as Node).value).toBe(5)
@@ -304,6 +317,7 @@ describe('LinkedList class', () => {
         .append(3)
       linkedList.insert(5, 1, 'before')
 
+      expect(linkedList.length).toBe(5)
       expect(linkedList.toString()).toBe('5,1,2,1,3')
       expect((linkedList.head as Node).value).toBe(5)
       expect((linkedList.tail as Node).value).toBe(3)
@@ -317,6 +331,7 @@ describe('LinkedList class', () => {
         .append(3)
       linkedList.insert(5, 3, 'before')
 
+      expect(linkedList.length).toBe(5)
       expect(linkedList.toString()).toBe('1,2,1,5,3')
       expect((linkedList.head as Node).value).toBe(1)
       expect((linkedList.tail as Node).value).toBe(3)
@@ -329,6 +344,7 @@ describe('LinkedList class', () => {
         .append(3)
       linkedList.insert(5, 4, 'before')
 
+      expect(linkedList.length).toBe(3)
       expect(linkedList.toString()).toBe('1,2,3')
     })
 
@@ -337,11 +353,13 @@ describe('LinkedList class', () => {
       expect(linkedList.toString()).toBe('')
       expect(linkedList.head).toBe(null)
       expect(linkedList.tail).toBe(null)
+      expect(linkedList.length).toBe(0)
 
       linkedList.insert(5, 3, 'before')
       expect(linkedList.toString()).toBe('')
       expect(linkedList.head).toBe(null)
       expect(linkedList.tail).toBe(null)
+      expect(linkedList.length).toBe(0)
     })
   })
 
@@ -354,6 +372,7 @@ describe('LinkedList class', () => {
       const reversaledList = linkedList.reversal()
       expect(reversaledList).toBeDefined()
       expect(reversaledList).toBeInstanceOf(LinkedList)
+      expect(linkedList.length).toBe(3)
       expect(reversaledList.toString()).toBe('3,2,1')
       expect((reversaledList.head as Node).value).toBe(3)
       expect((reversaledList.tail as Node).value).toBe(1)
@@ -366,6 +385,7 @@ describe('LinkedList class', () => {
       expect(reversaledList.toString()).toBe('')
       expect(reversaledList.head).toBe(null)
       expect(reversaledList.tail).toBe(null)
+      expect(linkedList.length).toBe(0)
     })
   })
 })

src/linked-list/index.ts

@@ -7,10 +7,16 @@ const stringifyDefault = (value: any) => {
 export class LinkedList {
   public head: Node | null
   public tail: Node | null
+  private _length: number
 
   constructor() {
     this.head = null
     this.tail = null
+    this._length = 0
+  }
+
+  public get length() {
+    return this._length
   }
 
   /**
@@ -19,6 +25,8 @@ export class LinkedList {
    * @returns {LinkedList} 当前链表
    */
   public append(value: any): LinkedList {
+    this._length++
+
     const newNode = new Node(value)
 
     if (!this.head) {
@@ -42,6 +50,8 @@ export class LinkedList {
    * @returns {LinkedList} 当前链表
    */
   public prepend(value: any): LinkedList {
+    this._length++
+
     const newNode = new Node(value)
 
     if (!this.head) {
@@ -88,6 +98,7 @@ export class LinkedList {
       }
 
       if (currentNode) {
+        this._length++
         const newNode = new Node(value, currentNode.next)
         if (currentNode === this.tail) {
           this.tail = newNode
@@ -99,6 +110,7 @@ export class LinkedList {
 
       if (currentNode) {
         if (targetValue === currentNode.value) {
+          this._length++
           const newNode = new Node(value, this.head)
           this.head = newNode
         } else {
@@ -113,6 +125,7 @@ export class LinkedList {
           }
 
           if (prevNode) {
+            this._length++
             const newNode = new Node(value, prevNode.next)
             prevNode.next = newNode
           }
@@ -139,6 +152,7 @@ export class LinkedList {
     // 查看head是不是需要删除的node
     while (this.head && this.head.value === value) {
       deletedNode = this.head
+      this._length--
       this.head = this.head.next
     }
 
@@ -148,6 +162,7 @@ export class LinkedList {
     while (currentNode !== null && currentNode.next) {
       if (currentNode.next.value === value) {
         deletedNode = currentNode.next
+        this._length--
         currentNode.next = currentNode.next.next
       } else {
         currentNode = currentNode.next
@@ -171,6 +186,7 @@ export class LinkedList {
     const headNode = this.head
 
     if (headNode !== null) {
+      this._length--
       deletedNode = headNode
       if (this.head === this.tail) {
         this.head = null
@@ -193,13 +209,15 @@ export class LinkedList {
     if (this.head !== null) {
       if (this.head === this.tail) {
         deletedNode = this.head
+        this._length--
         this.head = null
         this.tail = null
       } else {
         let currentNode = this.head
         while (currentNode.next !== null) {
           if (currentNode.next.next === null) {
             deletedNode = currentNode.next.next
+            this._length--
             currentNode.next = null
           } else {
             currentNode = currentNode.next