merge: Iterator and log methods added for linked lists (#891)

* iterator, log methods added in SL

* iterator, log methods added in DL

* test file added for DoublyLL

* format issue fix

Data-Structures/Linked-List/DoublyLinkedList.js

@@ -194,6 +194,30 @@ function DoubleLinkedList () {
   this.getTail = function () {
     return tail
   }
+
+  // Method to iterate over the LinkedList
+  this.iterator = function () {
+    let currentNode = this.getHead()
+    if (currentNode === null) return -1
+
+    const iterate = function * () {
+      while (currentNode) {
+        yield currentNode.element
+        currentNode = currentNode.next
+      }
+    }
+    return iterate()
+  }
+
+  // Method to log the LinkedList, for debugging
+  // it' a circular structure, so can't use stringify to debug the whole structure
+  this.log = function () {
+    let currentNode = this.getHead()
+    while (currentNode) {
+      console.log(currentNode.element)
+      currentNode = currentNode.next
+    }
+  }
 }
 
 // Example
@@ -202,5 +226,9 @@ function DoubleLinkedList () {
 // newDoubleLinkedList.append(1)
 // newDoubleLinkedList.append(2)
 // newDoubleLinkedList.size() // returns 2
+// const iterate = newDoubleLinkedList.iterator()
+// console.log(iterate.next().value) // 1
+// console.log(iterate.next().value) // 2
+// console.log(newDoubleLinkedList.log())
 
 export { DoubleLinkedList }

Data-Structures/Linked-List/SinglyLinkedList.js

@@ -211,6 +211,25 @@ class LinkedList {
 
     return list
   }
+
+  // Method to iterate over the LinkedList
+  iterator () {
+    let currentNode = this.headNode
+    if (currentNode === null) return -1
+
+    const iterate = function * () {
+      while (currentNode) {
+        yield currentNode.data
+        currentNode = currentNode.next
+      }
+    }
+    return iterate()
+  }
+
+  // Method to log the LinkedList
+  log () {
+    console.log(JSON.stringify(this.headNode, null, 2))
+  }
 }
 
 export { Node, LinkedList }

Data-Structures/Linked-List/test/DoublyLinkedList.test.js

@@ -0,0 +1,127 @@
+import { DoubleLinkedList } from '../DoublyLinkedList'
+
+describe('DoubleLinkedList', () => {
+  it('Check append', () => {
+    const list = new DoubleLinkedList()
+
+    list.append(1)
+    expect(list.getHead().element).toEqual(1)
+
+    list.append(2)
+    expect(list.getTail().element).toEqual(2)
+  })
+
+  it('Check insert', () => {
+    const list = new DoubleLinkedList()
+
+    list.insert(0, 1)
+    expect(list.getHead().element).toEqual(1)
+
+    list.insert(1, 20)
+    expect(list.getTail().element).toEqual(20)
+  })
+
+  it('Check removeAt', () => {
+    const list = new DoubleLinkedList()
+
+    list.insert(0, 10)
+    list.insert(1, 40)
+    list.insert(2, 30)
+
+    list.removeAt(0)
+    expect(list.getHead().element).toEqual(40)
+
+    list.removeAt(1)
+    expect(list.getTail().element).toEqual(40)
+  })
+
+  it('Check delete', () => {
+    const list = new DoubleLinkedList()
+
+    list.insert(0, 10)
+    list.insert(1, 40)
+
+    list.delete(10)
+    expect(list.getHead().element).toEqual(40)
+  })
+
+  it('Check deleteTail', () => {
+    const list = new DoubleLinkedList()
+
+    list.insert(0, 10)
+    list.insert(1, 40)
+
+    list.deleteTail()
+    expect(list.getTail().element).toEqual(10)
+  })
+
+  it('Check toString', () => {
+    const list = new DoubleLinkedList()
+
+    list.insert(0, 20)
+    expect(list.toString()).toEqual('20')
+  })
+
+  it('Check isEmpty', () => {
+    const list = new DoubleLinkedList()
+
+    expect(list.isEmpty()).toEqual(true)
+
+    list.insert(0, 'Hello')
+    expect(list.isEmpty()).toEqual(false)
+  })
+
+  it('Check size', () => {
+    const list = new DoubleLinkedList()
+    expect(list.size()).toBe(0)
+
+    list.append(10)
+    expect(list.size()).toBe(1)
+
+    list.removeAt(1)
+    expect(list.size()).toBe(1)
+  })
+
+  it('Check toArray', () => {
+    const list = new DoubleLinkedList()
+    list.append(1)
+    list.append(2)
+
+    const listArray = list.toArray()
+    expect(listArray).toEqual([1, 2])
+  })
+
+  it('Check getHead', () => {
+    const list = new DoubleLinkedList()
+    expect(list.getHead()).toEqual(null)
+
+    list.append(1)
+    list.append(2)
+    expect(list.getHead()).toBeInstanceOf(Object)
+  })
+
+  it('Check Iterator', () => {
+    const list = new DoubleLinkedList()
+
+    let iterate = list.iterator()
+    expect(iterate).toBe(-1)
+
+    const arr = [10, 20, 5]
+    list.append(arr[0])
+    list.append(arr[1])
+    list.append(arr[2])
+    iterate = list.iterator()
+
+    for (let i = 0; i < arr.length; i++) {
+      expect(iterate.next().value).toBe(arr[i])
+    }
+    expect(iterate.next().value).toBe(undefined)
+
+    iterate = list.iterator()
+    let count = 0
+    for (const item of iterate) {
+      expect(item).toBe(arr[count])
+      count++
+    }
+  })
+})

Data-Structures/Linked-List/test/SinglyLinkedList.test.js

@@ -163,4 +163,29 @@ describe('SinglyLinkedList', () => {
     list.removeFirst()
     expect(list.size()).toBe(1)
   })
+
+  it('Check Iterator', () => {
+    const list = new LinkedList()
+
+    let iterate = list.iterator()
+    expect(iterate).toBe(-1)
+
+    const arr = [10, 20, 5]
+    list.addLast(arr[0])
+    list.addLast(arr[1])
+    list.addLast(arr[2])
+    iterate = list.iterator()
+
+    for (let i = 0; i < arr.length; i++) {
+      expect(iterate.next().value).toBe(arr[i])
+    }
+    expect(iterate.next().value).toBe(undefined)
+
+    iterate = list.iterator()
+    let count = 0
+    for (const item of iterate) {
+      expect(item).toBe(arr[count])
+      count++
+    }
+  })
 })