Merge pull request #128 from hmizz/add-doublylinkedlist

Add doublylinkedlist

DIRECTORY.md

@@ -23,13 +23,15 @@
     * [MinPriorityQueue](https://github.com/TheAlgorithms/Javascript/blob/master/Data%20Structures/Heap/MinPriorityQueue.js)
   * Linked List
     * [singlylinklist](https://github.com/TheAlgorithms/Javascript/blob/master/Data%20Structures/Linked%20List/singlylinklist.js)
+    * [doublylinkedlist](https://github.com/TheAlgorithms/Javascript/blob/master/Data%20Structures/Linked%20List/doublylinkedlist.js)
   * Queue
     * [Queue](https://github.com/TheAlgorithms/Javascript/blob/master/Data%20Structures/Queue/Queue.js)
   * Stack
     * [Stack](https://github.com/TheAlgorithms/Javascript/blob/master/Data%20Structures/Stack/Stack.js)
   * Tree
     * [Binary Search Tree](https://github.com/TheAlgorithms/Javascript/blob/master/Data%20Structures/Tree/Binary%20Search%20Tree.js)
-
+     
+    
 ## Hashes
   * [SHA1](https://github.com/TheAlgorithms/Javascript/blob/master/Hashes/SHA1.js)
   * [SHA256](https://github.com/TheAlgorithms/Javascript/blob/master/Hashes/SHA256.js)

Data Structures/Linked List/DoublyLinkedList.js

@@ -0,0 +1,197 @@
+//Hamza chabchoub contribution for a university project 
+function doubleLinkedList() {
+    let Node = function(element) {
+      this.element = element;
+      this.next = null;
+      this.prev = null;
+    }
+    
+    let length = 0;
+    let head = null;
+    let tail = null;
+    
+    //Add new element
+    this.append = function(element) {
+      let node = new Node(element);
+      
+      if(!head){
+            head = node;
+            tail = node;
+       }else{
+         node.prev = tail;
+         tail.next = node;
+         tail = node;
+       }
+      
+      length++;
+    }
+    
+    
+    //Add element 
+    this.insert = function(position, element) {
+      
+      //Check of out-of-bound values
+      if(position >= 0 && position <= length){
+        let node = new Node(element),
+            current = head,
+            previous,
+            index = 0;
+        
+        if(position === 0){
+          if(!head){
+            head = node;
+            tail = node;
+          }else{
+            node.next = current;
+            current.prev = node;
+            head = node;
+          }
+        }else if(position === length){
+          current = tail;
+          current.next = node;
+          node.prev = current;
+          tail = node;
+        }else{
+          while(index++ < position){
+            previous = current;
+            current = current.next;
+          }
+          
+          node.next = current;
+          previous.next = node;
+          
+          //New
+          current.prev = node;
+          node.prev = previous; 
+        }
+        
+        length++;
+        return true;
+      }else{
+        return false;
+      }
+    }
+    
+    //Remove element at any position
+    this.removeAt = function(position){
+      //look for out-of-bounds value
+      if(position > -1 && position < length){
+        let current = head, previous, index = 0;
+        
+        //Removing first item
+        if(position === 0){
+          head = current.next;
+          
+          //if there is only one item, update tail //NEW
+          if(length === 1){
+            tail = null;
+          }else{
+            head.prev = null;
+          }
+        }else if(position === length - 1){
+          current = tail;
+          tail = current.prev;
+          tail.next = null;
+        }else{
+          while(index++ < position){
+            previous = current;
+            current = current.next;
+          }
+          
+          //link previous with current's next - skip it
+          previous.next = current.next; 
+          current.next.prev = previous;
+        }
+        
+        length--;
+        return current.element;
+      }else{
+        return null;
+      }
+    }
+    
+    //Get the indexOf item 
+    this.indexOf = function(elm){
+      let current = head,
+      index = -1;
+  
+      //If element found then return its position
+      while(current){
+        if(elm === current.element){
+           return ++index;
+        }
+  
+         index++;
+         current = current.next;
+       }
+  
+      //Else return -1
+      return -1;
+    };
+    
+    //Find the item in the list
+    this.isPresent = (elm) => {
+      return this.indexOf(elm) !== -1;
+    };
+    
+    //Delete an item from the list
+    this.delete = (elm) => {
+       return this.removeAt(this.indexOf(elm));
+    };  
+    
+    //Delete first item from the list
+    this.deleteHead = function(){
+      this.removeAt(0);
+    }
+    
+    //Delete last item from the list
+    this.deleteTail = function(){
+      this.removeAt(length-1);
+    }
+    
+    //Print item of the string
+    this.toString = function(){
+      let current = head,
+      string = '';
+  
+      while(current){
+        string += current.element + (current.next ? '\n' : '');
+        current = current.next;
+      }
+  
+      return string;
+    };
+    
+    //Convert list to array
+    this.toArray = function(){
+      let arr = [],
+      current = head;
+  
+      while(current){
+        arr.push(current.element);
+        current = current.next;
+      }
+  
+      return arr;
+    };
+    
+    //Check if list is empty
+    this.isEmpty = function(){
+      return length === 0;
+    };
+    
+    //Get the size of the list
+    this.size = function(){
+      return length;
+    }
+    
+    //Get the head
+    this.getHead = function() {
+      return head;
+    }
+    
+    //Get the tail
+    this.getTail = function() {
+      return tail;
+    }
+  }