doubly linked list

Author: deepakparamesh

2 Doubly_Linked_List.js

@@ -0,0 +1,135 @@
+class Node{
+    constructor(val){
+        this.val = val;
+        this.next = null;
+        this.prev = null;
+    }
+}
+
+
+class DoublyLinkedList {
+    constructor(){
+        this.head = null;
+        this.tail = null;
+        this.length = 0;
+    }
+    push(val){
+        var newNode = new Node(val);
+        if(this.length === 0){
+            this.head = newNode;
+            this.tail = newNode;
+        } else {
+            this.tail.next = newNode;
+            newNode.prev = this.tail;
+            this.tail = newNode;
+        }
+        this.length++;
+        return this;
+    } 
+    pop(){
+        if(!this.head) return undefined;
+        var poppedNode = this.tail;
+        if(this.length === 1){
+            this.head = null;
+            this.tail = null;
+        } else {
+            this.tail = poppedNode.prev;
+            this.tail.next = null;
+            poppedNode.prev = null;
+        }
+        this.length--;
+        return poppedNode;
+    }
+    shift(){
+        if(this.length === 0) return undefined;
+        var oldHead = this.head;
+        if(this.length === 1){
+            this.head = null;
+            this.tail = null;
+        }else{
+            this.head = oldHead.next;
+            this.head.prev = null;
+            oldHead.next = null;
+        }
+        this.length--;
+        return oldHead;
+    }
+    unshift(val){
+        var newNode = new Node(val);
+        if(this.length === 0) {
+            this.head = newNode;
+            this.tail = newNode;
+        } else {
+            this.head.prev = newNode;
+            newNode.next = this.head;
+            this.head = newNode;
+        }
+        this.length++;
+        return this;
+    }
+    get(index){
+        if(index < 0 || index >= this.length) return null;
+        var count, current;
+        if(index <= this.length/2){
+            count = 0;
+            current = this.head;
+            while(count !== index){
+                current = current.next;
+                count++;
+            }
+        } else {
+            count = this.length - 1;
+            current = this.tail;
+            while(count !== index){
+                current = current.prev;
+                count--;
+            }
+        }
+        return current;
+    }
+    set(index, val){
+        var foundNode = this.get(index);
+        if(foundNode != null){
+            foundNode.val = val;
+            return true;
+        }
+        return false;
+    }
+    insert(index, val){
+        if(index < 0 || index > this.length) return false;
+        if(index === 0) return !!this.unshift(val);
+        if(index === this.length) return !!this.push(val);
+
+        var newNode = new Node(val);
+        var beforeNode = this.get(index-1);
+        var afterNode = beforeNode.next;
+        
+        beforeNode.next = newNode, newNode.prev = beforeNode;
+        newNode.next = afterNode, afterNode.prev = newNode;
+        this.length++;
+        return true;
+    }
+    remove(index) {
+        if (index < 0 || index >= this.length) return false;
+        if(index === 0) return !!this.shift();
+        if (index === this.length) return !!this.pop();
+
+        var removeNode = this.get(index);
+        var beforeNode = removeNode.prev;
+        var afterNode = removeNode.next;
+
+        beforeNode.next = afterNode;
+        afterNode.prev = beforeNode;
+
+        removeNode.next = null;
+        removeNode.prev = null;
+
+        this.length--;
+        return removeNode;
+    }
+}
+
+var list = new DoublyLinkedList()
+list.push("Harry")
+list.push("Ron")
+list.push("Hermione")