feat(LinkedList): add reverse

sun0day · Oct 12, 2022 · b0b8536 · b0b8536
1 parent 626db0d
commit b0b8536
Show file tree

Hide file tree

Showing 2 changed files with 36 additions and 0 deletions.
diff --git a/packages/linked-list/index.test.ts b/packages/linked-list/index.test.ts
@@ -113,4 +113,20 @@ describe('LinkedList', () => {
     expect(list.size()).toBe(0)
     expect(list.toArray()).toEqual([])
   })
+
+  it('should reverse', () => {
+    let list = new LinkedList()
+    list.reverse()
+    expect(list.toArray()).toEqual([])
+
+    list = LinkedList.from([1])
+    list.reverse()
+    expect(list.toArray()).toEqual([1])
+    expect(list.tail().value).toBe(1)
+
+    list = LinkedList.from([1, 2, 3])
+    list.reverse()
+    expect(list.toArray()).toEqual([3, 2, 1])
+    expect(list.tail().value).toBe(1)
+  })
 })
diff --git a/packages/linked-list/index.ts b/packages/linked-list/index.ts
@@ -174,6 +174,26 @@ export class LinkedList<T> {
     return cur
   }
 
+  /**
+   * reverse a linked list, T = O(n)
+   *
+   * @returns {LinkedList<T>} - linked list after reverse
+   */
+  reverse() {
+    let prev = null; let cur = this._head; let next = null
+
+    while (cur) {
+      next = cur.next
+      cur.next = prev
+
+      prev = cur
+      cur = next
+    }
+
+    this._tail = this._head
+    this._head = prev
+  }
+
   /**
    * get head node
    *