Added reverse() method to LinkedList

src/linkedList.d.ts

@@ -21,4 +21,5 @@ export class LinkedList<T> {
   isEmpty(): boolean;
   clear(): void;
   static fromArray<T>(values: (T extends LinkedListNode ? T : LinkedListNode)[]): LinkedList<T>;
+  reverse(): LinkedList<T>;
 }

src/linkedList.js

@@ -340,6 +340,30 @@ class LinkedList {
     });
     return linkedList;
   }
-}
+  /**
+   * Reverses the linked list in-place.
+   * @public
+   * @returns {LinkedList}
+   */
+  reverse() {
+    if (this.isEmpty() || !this._head.hasNext()) {
+      return this; // no change needed
+    }
 
+    let prev = null;
+    let current = this._head;
+    let next = null;
+
+    while (current instanceof LinkedListNode) {
+      next = current.getNext();   // store next
+      current.setNext(prev);      // reverse pointer
+      prev = current;             // move prev
+      current = next;             // move current
+    }
+
+    this._head = prev;
+    return this;
+  }
+
+}
 exports.LinkedList = LinkedList;

test/linkedList.test.js

@@ -215,4 +215,35 @@ describe('linkedList tests', () => {
       ]);
     });
   });
+
+  describe('.reverse()', () => {
+  it('reverse the linked list order', () => {
+    const list = new LinkedList();
+    list.insertLast(1);
+    list.insertLast(2);
+    list.insertLast(3);
+    list.insertLast(4);
+
+    list.reverse();
+
+    expect(list.toArray().map(n => n.getValue()))
+      .to.deep.equal([4, 3, 2, 1]);
+  });
+
+  it('reverse an empty list', () => {
+    const list = new LinkedList();
+    list.reverse();
+    expect(list.toArray()).to.deep.equal([]);
+  });
+
+  it('reverse a single-node list', () => {
+    const list = new LinkedList();
+    list.insertLast(99);
+    list.reverse();
+
+    expect(list.toArray().map(n => n.getValue()))
+      .to.deep.equal([99]);
+  });
+});
+
 });