Merge 49a86ecb31 into 4b6450ab84

utilities/javascript/doublyLinkedList.js

@@ -0,0 +1,114 @@
+/*
+ * Doubly LinkedList with functionalities of 
+   * add: Add node to list
+   * contains: Check if the list contains a certain value (Not a strict object comparison)
+   * getCurrentNode
+   * toString(): Prints the LinkedList representation
+   * next()
+   * previous()
+*/
+class Node {
+  constructor(_value) {
+    this.value = _value;
+    this.next = null;
+    this.previous = null;
+  }
+  setNext(_next) {
+    this.next = _next;
+  }
+  setPrevious(_previous) {
+  	this.previous = _previous;
+  }
+}
+class LinkedList {
+  constructor() {
+  	this.currentNode = null;
+  	this.firstNode = null;
+  	this.lastNode = null;
+    for (let i = 0; i < arguments.length; i++) {
+      this.add(arguments[i]);
+    }
+    // Update lastNode as currentNode after init.
+    this.currentNode = this.lastNode;
+  }
+  add(element) {
+    // Construct new node
+    let newNode = new Node(element);
+    // Update global list
+    this.update(newNode);
+    // Link up
+    if (this.lastNode) {
+      this.lastNode.setNext(newNode);
+      newNode.setPrevious(this.lastNode);
+    } else {
+      // Is first node
+      this.firstNode = newNode;
+    }
+    // Update currentNode
+    this.lastNode = newNode;
+  }
+  contains(element) {
+    if (this.globalList[element]) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+  // Helper function to update global list
+  update(newNode) {
+    if (this.globalList) { // Has existing
+      this.globalList[newNode.value] = true;
+    } else {
+      // Brand new
+      this.globalList = {}
+      this.globalList[newNode.value] = true;
+    }
+  }
+  getCurrentNode() {
+  	return this.currentNode;
+  }
+  next() {
+  	if (this.currentNode.next) {
+  		this.currentNode = this.currentNode.next;
+  	} else {
+  		console.log('Already at end of linked list'); // Optionally, go back to first element if we want a doubly-circular linkedlist
+  	}
+  }
+  previous() {
+  	if (this.currentNode.previous) {
+  		this.currentNode = this.currentNode.previous;
+  	} else {
+  		console.log('Already at start of linked list'); // Optionally, go back to first element if we want a doubly-circular linkedlist
+  	}
+  }
+  toString() {
+  	var nodeToPrint = this.firstNode;
+  	var linkedListString = String(nodeToPrint.value);
+  	while(nodeToPrint.next) {
+  		nodeToPrint = nodeToPrint.next;
+  		linkedListString += "->";
+  		linkedListString += String(nodeToPrint.value);
+  	}
+  	return linkedListString;
+  }
+}
+
+
+/* Tests */
+var list = new LinkedList(1,2,3); // New DoublyLinkedList constructed with value 1->2->3
+console.log(list.toString()); // Prints '1->2->3'
+list.contains(2); // returns true
+list.contains(4); // returns false
+console.log(list.currentNode.value); // Returns 3
+list.previous(); // Pointer moves back by 1
+console.log(list.currentNode.value); // Returns 2
+list.next(); // Pointer moves forward by 1
+console.log(list.currentNode.value); // Returns 3
+list.next(); // Pointer moves forward by 1, but already at end of list. 'Already at end of linked list' logs to console.
+list.previous(); // Pointer moves back by 1
+list.previous(); // Pointer moves back by 1
+console.log(list.currentNode.value); // Returns 1
+list.previous(); // Pointer moves back by 1, but already at start of list. 'Already at start of linked list' logs to console.
+list.add(4); // List is now 1->2->3->4
+list.contains(4); // returns true
+console.log(list.toString()); // Prints '1->2->3->4'