Update linked-list.js

src/linked-list.js

@@ -1,74 +1,126 @@
 const Node = require('./node');
-//не понял условие продерки метода append ( _head, _tail)
-
-class LinkedList extends Node {
+class LinkedList {
     constructor() {
-        super()
-        this.arr = [];
-        this.length = this.arr.length;        
+      this.list = [];
+      this.length = 0;
+      this._head = null;
+      this._tail = null;
     }
 
-    append(data) {        
-        this.arr.push(data);
-        this.length = this.arr.length;
-        return this;
-
+    append(data) {
+      if (this.length == 0) {
+        this.list[0] = new Node(data);
+        this.length = 1;
+        this._tail = this.list[0];
+        this._head = this.list[0];
+      } else {
+        this.list[this.length] = new Node(data, this.list[this.length -1].data);
+        this.list[this.length -1].next =  this.list[this.length].data;
+        this.length = this.list.length;
+        this._tail = this.list[this.length - 1];          
+      }
+      return this;
     }
 
-    head() {        
-        if (this.arr[0]) {
-            return this.arr[0];
-        } else {
-            return null;
-        }
+    head() {
+      if (this.length == 0) {
+        return null;
+      }
+      return this._head.data;
     }
 
-    tail() {        
-        if (this.arr[this.arr.length - 1]) {
-            return this.arr[this.arr.length - 1];
-        } else {
-            return null;
-        }
+    tail() {
+      if (this.length == 0) {
+        return null;
+      }
+      return this._tail.data;
     }
 
-    at(index) {         
-        return this.arr[index];
+    at(index) {
+      return this.list[index].data;
     }
 
     insertAt(index, data) {
-        this.arr[index] = data;
-        this.length = this.arr.length;
-         return this;
+      if (this.length == 0) {
+        this.append(data);
+      } else if ((this.length - 1 ) == index){
+          this.list[index].data = data;
+          this.list[index - 1].next = data;
+      } else {
+        this.list[index].data = data;
+        if ((this.list[index - 1].next) != null) {
+          this.list[index - 1].next = data;
+        }
+        if ((this.list[index + 1].prev) != null) {
+          this.list[index + 1].prev = data;
+        }
+      }
     }
 
-    isEmpty() {        
-        if (this.arr == 0) {
-            return true;
-        } else {
-            return false;
-        }
+    isEmpty() {
+      if (this.length == 0) {
+        return true;
+      }
+      return false;
     }
 
     clear() {
-        this.length = 0;
-        this.arr.length = 0;
-         return this;        
+      this.list = [];
+      this.length = 0;
+      this._head = null;
+      this._tail = null;
+      return this;
     }
 
-    deleteAt(index) {         
-        this.arr.splice(index, 1);
-        this.length = this.arr.length;
-         return this;       
+    deleteAt(index) {
+      if ((this.length == 1) && (index == 0)) {
+        this.clear()
+      } else {
+        if (index == 0) {
+          this.list[index + 1].prev = null;
+          this.list.splice(index, 1);
+          this.length -= 1;
+          return this
+        }
+        if (index == this.list.length) {
+          this.list[index - 1].next = null;
+          this.list.splice(index, 1);
+          this.length -= 1;
+          return this
+        }
+        this.list[index - 1].next = this.list[index + 1].data;
+        this.list[index + 1].prev = this.list[index - 1].data;
+        this.list.splice(index, 1);
+        this.length -= 1;
+      }
+      return this
     }
 
-    reverse() {         
-        Array.prototype.reverse.call(this.arr);        
-         return this;        
+    reverse() {
+      if (this.length > 1) {
+        this.list[0].next = null;
+        this.list[0].prev = this.list[1].data;
+        this.list[this.length - 1].next = this.list[this.length - 2].data
+        this.list[this.length - 1].prev = null;
+        this._tail = this.list[0];
+        this._head = this.list[this.length - 1];
+        for (var i = 1; i < (this.list.length - 1); i++) {
+          this.list[i].next = this.list[i - 1].data;
+          this.list[i].prev = this.list[i + 1].data;
+        }
+        this.list.reverse();
+      }
+      return this
     }
 
-    indexOf(data) {        
-        return this.arr.indexOf(data);        
+    indexOf(data) {
+      for (var i = 0; i < this.list.length; i++) {
+        if ( this.list[i].data == data ) {
+          return i;
+        }
+      }
+      return -1;
     }
-}
+  }
 
 module.exports = LinkedList;