Add solution #707

Author: JoshCrozier

0707-design-linked-list.js

@@ -0,0 +1,110 @@
+/**
+ * 707. Design Linked List
+ * https://leetcode.com/problems/design-linked-list/
+ * Difficulty: Medium
+ *
+ * Design your implementation of the linked list. You can choose to use a singly or
+ * doubly linked list.
+ *
+ * A node in a singly linked list should have two attributes: val and next. val is the value
+ * of the current node, and next is a pointer/reference to the next node.
+ *
+ * If you want to use the doubly linked list, you will need one more attribute prev to indicate
+ * the previous node in the linked list. Assume all nodes in the linked list are 0-indexed.
+ *
+ * Implement the MyLinkedList class:
+ * - MyLinkedList() Initializes the MyLinkedList object.
+ * - int get(int index) Get the value of the indexth node in the linked list. If the
+ *   index is invalid, return -1.
+ * - void addAtHead(int val) Add a node of value val before the first element of the
+ *   linked list. After the insertion, the new node will be the first node of the linked list.
+ * - void addAtTail(int val) Append a node of value val as the last element of the linked list.
+ * - void addAtIndex(int index, int val) Add a node of value val before the indexth node
+ *   in the linked list. If index equals the length of the linked list, the node will be
+ *   appended to the end of the linked list. If index is greater than the length, the node
+ *   will not be inserted.
+ * - void deleteAtIndex(int index) Delete the indexth node in the linked list, if the index
+ *   is valid.
+ */
+
+var MyLinkedList = function() {
+  this.head = null;
+  this.size = 0;
+};
+
+/**
+ * @param {number} index
+ * @return {number}
+ */
+MyLinkedList.prototype.get = function(index) {
+  if (index < 0 || index >= this.size) return -1;
+  let current = this.head;
+  while (index--) current = current.next;
+  return current.val;
+};
+
+/**
+ * @param {number} val
+ * @return {void}
+ */
+MyLinkedList.prototype.addAtHead = function(val) {
+  const node = new Node(val);
+  node.next = this.head;
+  this.head = node;
+  this.size++;
+};
+
+/**
+ * @param {number} val
+ * @return {void}
+ */
+MyLinkedList.prototype.addAtTail = function(val) {
+  const node = new Node(val);
+  if (!this.head) {
+    this.head = node;
+  } else {
+    let current = this.head;
+    while (current.next) current = current.next;
+    current.next = node;
+  }
+  this.size++;
+};
+
+/**
+ * @param {number} index
+ * @param {number} val
+ * @return {void}
+ */
+MyLinkedList.prototype.addAtIndex = function(index, val) {
+  if (index < 0 || index > this.size) return;
+  if (index === 0) return this.addAtHead(val);
+  const node = new Node(val);
+  let current = this.head;
+  while (--index) current = current.next;
+  node.next = current.next;
+  current.next = node;
+  this.size++;
+};
+
+/**
+ * @param {number} index
+ * @return {void}
+ */
+MyLinkedList.prototype.deleteAtIndex = function(index) {
+  if (index < 0 || index >= this.size) return;
+  this.size--;
+  if (index === 0) {
+    this.head = this.head.next;
+    return;
+  }
+  let current = this.head;
+  while (--index) current = current.next;
+  current.next = current.next.next;
+};
+
+class Node {
+  constructor(val) {
+    this.val = val;
+    this.next = null;
+  }
+}

README.md

@@ -535,6 +535,7 @@
 704|[Binary Search](./0704-binary-search.js)|Easy|
 705|[Design HashSet](./0705-design-hashset.js)|Easy|
 706|[Design HashMap](./0706-design-hashmap.js)|Easy|
+707|[Design Linked List](./0707-design-linked-list.js)|Medium|
 713|[Subarray Product Less Than K](./0713-subarray-product-less-than-k.js)|Medium|
 714|[Best Time to Buy and Sell Stock with Transaction Fee](./0714-best-time-to-buy-and-sell-stock-with-transaction-fee.js)|Medium|
 717|[1-bit and 2-bit Characters](./0717-1-bit-and-2-bit-characters.js)|Easy|