From a23ed05d93236cc6f84851ebddc7460cbf080ce4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=91=A8=E6=98=9F=E6=98=9F=E2=9C=A8?=
 <if.true.else@gmail.com>
Date: Tue, 29 Apr 2025 07:49:24 +0800
Subject: [PATCH] :bug: fix(go/09_queue): Fix the linked list queue.

When all of the nodes are dequeue, keep the head and tail the same.
---
 go/09_queue/QueueBasedOnLinkedList.go      |  7 +++++++
 go/09_queue/QueueBasedOnLinkedList_test.go | 23 ++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/go/09_queue/QueueBasedOnLinkedList.go b/go/09_queue/QueueBasedOnLinkedList.go
index 65d898da..5e017b61 100644
--- a/go/09_queue/QueueBasedOnLinkedList.go
+++ b/go/09_queue/QueueBasedOnLinkedList.go
@@ -33,8 +33,15 @@ func (this *LinkedListQueue) DeQueue() interface{} {
 	if this.head == nil {
 		return nil
 	}
+
 	v := this.head.val
 	this.head = this.head.next
+
+	// fix: keep the head and tail the same
+	if this.head == nil {
+		this.tail = nil
+	}
+
 	this.length--
 	return v
 }
diff --git a/go/09_queue/QueueBasedOnLinkedList_test.go b/go/09_queue/QueueBasedOnLinkedList_test.go
index 425c6e8a..d45ca8b3 100644
--- a/go/09_queue/QueueBasedOnLinkedList_test.go
+++ b/go/09_queue/QueueBasedOnLinkedList_test.go
@@ -22,14 +22,37 @@ func TestListQueue_DeQueue(t *testing.T) {
 	q.EnQueue(5)
 	q.EnQueue(6)
 	t.Log(q)
+
+	// 1
+	q.DeQueue()
+	t.Log(q)
+
+	// 2
+	q.DeQueue()
+	t.Log(q)
+
+	// 3
 	q.DeQueue()
 	t.Log(q)
+
+	// 4
 	q.DeQueue()
 	t.Log(q)
+
+	// 5
 	q.DeQueue()
 	t.Log(q)
+
+	// 6 note: all of the nodes are dequeue
+	// head = tail = nil
 	q.DeQueue()
 	t.Log(q)
+
+	// enqueue
+	q.EnQueue(1)
+	t.Log(q)
+
+	// head = tail = nil
 	q.DeQueue()
 	t.Log(q)
 }