refactored from ES6 classes to factory function to Linked Lists types Data Strucutre

Author: crizstian

06-chapter-Linked-Lists-types/index.js

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+(function (exports) {
+  const {linked} = require('./linked.proto.module')
+
+  Object.assign(exports, {linked})
+}((typeof module.exports !== 'undefined') ? module.exports : window))

06-chapter-Linked-Lists-types/linked.proto.module.js

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+(function (exports) {
+  const node = (data) => {
+    const double = [].slice.call(arguments, 1)[0]
+    const nodeProto = {
+      data: 'data',
+      next: null
+    }
+    if (double === 'double') {
+      nodeProto.prev = null
+    }
+    return Object.assign(Object.create(nodeProto), {data})
+  }
+
+  // Helper functions
+  const curry = fn => (...args) => fn.bind(null, ...args)
+  const compose = (...fns) => data => fns.reduce((v, f) => f(v), data)
+
+  // Factory function
+  const linked = (type) => {
+
+    const link = {}
+    // private variables
+    let head = null
+    let current = null
+    let length = 0
+
+    // single responsability
+    const setHead = (data) => {
+      head = data
+      return head
+    }
+    const setHead2 = (data) => {
+      head = data
+      head.next = head
+      return head
+    }
+    const setCurrent = (data) => {
+      current = data
+      return current
+    }
+    const setLength = (type) => {
+      length += (type) ? 1 : -1
+    }
+
+    // Pure functions
+    const setNext = curry((value, data) => {
+      value.next = data
+      return data
+    })
+    const setPrev = curry((value, data) => {
+      if (data !== null) {
+        data.prev = value
+      }
+      return data
+    })
+    const setNext2 = curry((value, data) => {
+      if(data.next === null) {
+        value.next = head
+      }
+      value.next = data
+      return data
+    })
+    const setPrev2 = curry((value, data) => {
+      if (data === null) {
+        data = head
+      } else {
+        data.prev = value
+      }
+      return data
+    })
+
+    // linked list functions
+    const findPrev = (data) => {
+      let c = head
+      while (!(c.next === null)) {
+        if (c.next.data === data) {
+          return c
+        } else {
+          c = c.next
+        }
+      }
+      return false
+    }
+
+    const add = (data) => {
+      let args = (!head && !current) ? [setHead] : [setNext(current)]
+      compose(...args, setCurrent, setLength)(node(data))
+    }
+
+    const add2 = (data) => {
+      let args = (!head && !current) ? [setHead] : [setNext(current), setPrev(current)]
+      compose(...args, setCurrent, setLength)(node(data))
+    }
+
+    const add3 = (data) => {
+      let args = (!head && !current) ? [setHead2] : [setNext2(current), setPrev2(current)]
+      compose(...args, setCurrent, setLength)(node(data))
+    }
+
+    const remove = (data) => {
+      let prev = findPrev(data)
+      if (!(prev.next === null)) {
+        compose(setCurrent, setNext(prev))(prev.next.next)
+      }
+      setLength(false)
+    }
+
+    const remove2 = (data) => {
+      let prev = findPrev(data)
+      if (!(prev.next === null)) {
+        compose(setPrev(prev),setNext(prev), setCurrent)(prev.next.next)
+      }
+      setLength(false)
+    }
+
+    const remove3 = (data) => {
+      let prev = findPrev(data)
+      if (!(prev.next === null)) {
+        compose(setPrev2(prev),setNext2(prev), setCurrent)(prev.next.next)
+      }
+      setLength(false)
+    }
+
+    link.contains = (data) => {
+      let c = head
+      while (!(c === null)) {
+        if (c.data === data) {
+          return true
+        }
+        c = c.next
+      }
+      return false
+    }
+
+    const display = () => {
+      let c = head
+      let show = ''
+      while (!(c === null)) {
+        show += `${c.data} ${(c.next !== null) ? ' ->' : ''} `
+        c = c.next
+      }
+      return show
+    }
+
+    const display2 = () => {
+      let c = head
+      let show = `${c.data} -> `
+      while (!(c.next.data === head.data)) {
+        show += `${c.next.data} ${(c.data !== head.data) ? ' ->' : ''} `
+        c = c.next
+      }
+      return show
+    }
+
+    link.getCurrent = () => current
+    link.getList = () => head
+    link.size = () => length
+
+    // object prototype
+    const list = Object.create(link)
+
+    if (type === 'single') {
+      Object.assign(list, {add, display, remove})
+    } else if (type === 'double') {
+      Object.assign(list, {add: add2, display, remove: remove2})
+    } else {
+      Object.assign(list, {add: add3, display: display2, remove: remove3})
+    }
+
+    return list
+  }
+
+  Object.assign(exports, {linked})
+}((typeof module.exports !== undefined) ? module.exports : window))

06-chapter-Linked-Lists-types/readme.md

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+# Linked List, Double Linked List, Circular Linked List
+
+### Code Examples
+
+- [Linked List Data Structure]('./linked-list.module')
+- [Double Linked List Data Structure]('./double-linked-list.module')
+- [Circular Linked List Data Structure]('./circular-linked-list.module')
+- [Import complete module]('./index')
+
+### Definition Linked List
+
+The simplest form of linked lists — a singly linked list — is a series of nodes where each individual node contains both a value and a pointer to the next node in the list.
+
+common operations you can perform on linked list:
+
+**Additions**
+- `add`: grow the list by adding items to the end of the list.
+- `addHead`: Similar to our add method above, we always know the position of the head, so no iteration necessary.
+- `insertAfter`: have to iterate over the entire list to find the target node that your value should be inserted after.
+**Removals**
+- `remove`: will always remove from a given position in the list.
+
+**Search**
+- `contains`: will search the list for a value.
+
+### Definition Double Linked List
+
+Doubly Linked List is a variation of Linked list in which navigation is possible in both ways, either forward and backward easily as compared to Single Linked List. Following are the important terms to understand the concept of doubly linked list.
+
+- Link − Each link of a linked list can store a data called an element.
+
+- Next − Each link of a linked list contains a link to the next link called Next.
+
+- Prev − Each link of a linked list contains a link to the previous link called Prev.
+
+LinkedList − A Linked List contains the connection link to the first link called First and to the last link called Last.
+
+common operations you can perform on linked list:
+
+**Additions**
+- `add`: grow the list by adding items to the end of the list.
+- `addHead`: Similar to our add method above, we always know the position of the head, so no iteration necessary.
+- `insertAfter`: ave to iterate over the entire list to find the target node that your value should be inserted after.
+- `insertLast`: adds an element at the end of the list.
+**Removals**
+- `remove`: will always remove from a given position in the list.
+- `removeLast`: deletes an element from the end of the list.
+**Search**
+- `contains`: will search the list for a value.
+**Display**
+- `display`: displays the complete list in a forward manner.
+- `displayReverse`: displays the complete list in a backward manner.
+
+
+### Definition Circular Linked List
+
+Circular Linked List is a variation of Linked list in which the first element points to the last element and the last element points to the first element. Both Singly Linked List and Doubly Linked List can be made into a circular linked list.
+
+Singly Linked List as Circular
+
+In singly linked list, the next pointer of the last node points to the first node
+
+Doubly Linked List as Circular
+
+In doubly linked list, the next pointer of the last node points to the first node and the previous pointer of the first node points to the last node making the circular in both directions.
+
+common operations you can perform on linked list:
+
+**Additions**
+- `add`: grow the list by adding items to the end of the list.
+**Removals**
+- `remove`: will always remove from a given position in the list.
+**Search**
+- `contains`: will search the list for a value.
+**Display**
+- `display`: displays the complete list in a forward manner.
+
+### Example use cases
+- Storing values in a hash table to prevent collisions
+
+### Resources
+
+- [Data Structure and Algorithms - Linked List](https://www.tutorialspoint.com/data_structures_algorithms/linked_list_algorithms.htm)

06-chapter-Linked-Lists-types/test.js

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+const {linked} = require('./index')
+
+test('Linked List test', assert => {
+  const amazingRace = linked('single')
+
+  amazingRace.add('Colombo, Sri Lanka')
+  assert.equal(amazingRace.getCurrent().data, 'Colombo, Sri Lanka', 'can add an element')
+
+  amazingRace.add('Lagos, Nigeria')
+  amazingRace.add('Surat, India')
+  amazingRace.add('Suzhou, China')
+
+  assert.equal(4, amazingRace.size(), 'can get the size of the linked list')
+  console.log(`contains 'Suzhou, China' ? ${amazingRace.contains('Suzhou, China')}`) // true
+  console.log(`contains 'Hanoi, Vietnam' ? ${amazingRace.contains('Hanoi, Vietnam')}`) // true
+  amazingRace.add('Hanoi, Vietnam')
+  console.log(`contains 'Seattle, Washington' ? ${amazingRace.contains('Seattle, Washington')}`) // true
+  amazingRace.add('Seattle, Washington')
+  console.log(`contains 'North Pole' ? ${amazingRace.contains('North Pole')}`) // true
+  amazingRace.add('North Pole')
+
+  amazingRace.remove('North Pole')
+  amazingRace.remove('Hanoi, Vietnam')
+  assert.equal(amazingRace.size(), 5, 'can remove elements')
+})
+
+test('Double Linked List test', assert => {
+  const amazingRace = linked('double')
+
+  amazingRace.add('Colombo, Sri Lanka')
+
+  assert.equal(amazingRace.getCurrent().data, 'Colombo, Sri Lanka', 'can add an element')
+
+  amazingRace.add('Lagos, Nigeria')
+  amazingRace.add('Surat, India')
+  amazingRace.add('Suzhou, China')
+  assert.equal(amazingRace.getCurrent().prev.data, 'Surat, India', 'double linked list')
+})