linkedList.js 3.5 KB

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  1. /*---------------------------------------------------------------------------------------------
  2. * Copyright (c) Microsoft Corporation. All rights reserved.
  3. * Licensed under the MIT License. See License.txt in the project root for license information.
  4. *--------------------------------------------------------------------------------------------*/
  5. class Node {
  6. constructor(element) {
  7. this.element = element;
  8. this.next = Node.Undefined;
  9. this.prev = Node.Undefined;
  10. }
  11. }
  12. Node.Undefined = new Node(undefined);
  13. export class LinkedList {
  14. constructor() {
  15. this._first = Node.Undefined;
  16. this._last = Node.Undefined;
  17. this._size = 0;
  18. }
  19. get size() {
  20. return this._size;
  21. }
  22. isEmpty() {
  23. return this._first === Node.Undefined;
  24. }
  25. clear() {
  26. let node = this._first;
  27. while (node !== Node.Undefined) {
  28. const next = node.next;
  29. node.prev = Node.Undefined;
  30. node.next = Node.Undefined;
  31. node = next;
  32. }
  33. this._first = Node.Undefined;
  34. this._last = Node.Undefined;
  35. this._size = 0;
  36. }
  37. unshift(element) {
  38. return this._insert(element, false);
  39. }
  40. push(element) {
  41. return this._insert(element, true);
  42. }
  43. _insert(element, atTheEnd) {
  44. const newNode = new Node(element);
  45. if (this._first === Node.Undefined) {
  46. this._first = newNode;
  47. this._last = newNode;
  48. }
  49. else if (atTheEnd) {
  50. // push
  51. const oldLast = this._last;
  52. this._last = newNode;
  53. newNode.prev = oldLast;
  54. oldLast.next = newNode;
  55. }
  56. else {
  57. // unshift
  58. const oldFirst = this._first;
  59. this._first = newNode;
  60. newNode.next = oldFirst;
  61. oldFirst.prev = newNode;
  62. }
  63. this._size += 1;
  64. let didRemove = false;
  65. return () => {
  66. if (!didRemove) {
  67. didRemove = true;
  68. this._remove(newNode);
  69. }
  70. };
  71. }
  72. shift() {
  73. if (this._first === Node.Undefined) {
  74. return undefined;
  75. }
  76. else {
  77. const res = this._first.element;
  78. this._remove(this._first);
  79. return res;
  80. }
  81. }
  82. pop() {
  83. if (this._last === Node.Undefined) {
  84. return undefined;
  85. }
  86. else {
  87. const res = this._last.element;
  88. this._remove(this._last);
  89. return res;
  90. }
  91. }
  92. _remove(node) {
  93. if (node.prev !== Node.Undefined && node.next !== Node.Undefined) {
  94. // middle
  95. const anchor = node.prev;
  96. anchor.next = node.next;
  97. node.next.prev = anchor;
  98. }
  99. else if (node.prev === Node.Undefined && node.next === Node.Undefined) {
  100. // only node
  101. this._first = Node.Undefined;
  102. this._last = Node.Undefined;
  103. }
  104. else if (node.next === Node.Undefined) {
  105. // last
  106. this._last = this._last.prev;
  107. this._last.next = Node.Undefined;
  108. }
  109. else if (node.prev === Node.Undefined) {
  110. // first
  111. this._first = this._first.next;
  112. this._first.prev = Node.Undefined;
  113. }
  114. // done
  115. this._size -= 1;
  116. }
  117. *[Symbol.iterator]() {
  118. let node = this._first;
  119. while (node !== Node.Undefined) {
  120. yield node.element;
  121. node = node.next;
  122. }
  123. }
  124. }