From bb198fc73322d8c740d5c48f5fea9c97614eaa5c Mon Sep 17 00:00:00 2001
From: yanqizhao <zhaoyanqi703@hellobike.com>
Date: Thu, 28 Apr 2022 19:19:32 +0800
Subject: [PATCH 1/3] fix: fix the missing assignment of tail in
 copyNode(returningCopyOf:)

---
 .../projects/finished/LinkedList.playground/Contents.swift    | 4 ++++
 .../finished/LinkedList.playground/Sources/LinkedList.swift   | 1 +
 2 files changed, 5 insertions(+)

diff --git a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
index d41e150..5569c42 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
@@ -129,4 +129,8 @@ example(of: "linked list cow") {
     list2.remove(after: node)
   }
   print("List2: \(list2)")
+    
+    print("Append node on list2")
+    list2.append(4)
+    print("List2: \(list2)")
 }
diff --git a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
index ab44d82..4122fb6 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
@@ -135,6 +135,7 @@ public struct LinkedList<Value> {
       newNode = newNode!.next
       oldNode = nextOldNode
     }
+      tail = newNode
     
     return nodeCopy
   }

From aed019616cdf70f82e7a681e25c55f09ed7aed19 Mon Sep 17 00:00:00 2001
From: yanqizhao <zhaoyanqi703@hellobike.com>
Date: Thu, 28 Apr 2022 19:53:39 +0800
Subject: [PATCH 2/3] fix: add the missing copyNodes(returningCopyOf:) in
 insert(_:, after:)

---
 .../finished/LinkedList.playground/Contents.swift        | 9 ++++++++-
 .../LinkedList.playground/Sources/LinkedList.swift       | 4 ++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
index 5569c42..fce6265 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
@@ -38,7 +38,7 @@ example(of: "inserting at a particular index") {
   print("Before inserting: \(list)")
   var middleNode = list.node(at: 1)!
   for _ in 1...4 {
-    middleNode = list.insert(-1, after: middleNode)
+    middleNode = list.insert(-1, after: middleNode) ?? Node(value: 0)
   }
   print("After inserting: \(list)")
 }
@@ -133,4 +133,11 @@ example(of: "linked list cow") {
     print("Append node on list2")
     list2.append(4)
     print("List2: \(list2)")
+
+    print("Insert node on list2")
+    if let node2 = list2.node(at: 0) {
+      list2.insert(5, after: node2)
+    }
+    print("List2: \(list2)")
+
 }
diff --git a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
index 4122fb6..2c9439d 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
@@ -41,8 +41,8 @@ public struct LinkedList<Value> {
   }
   
   @discardableResult
-  public mutating func insert(_ value: Value, after node: Node<Value>) -> Node<Value> {
-    copyNodes()
+  public mutating func insert(_ value: Value, after node: Node<Value>) -> Node<Value>? {
+    guard let node = copyNodes(returningCopyOf: node) else { return nil }
     guard tail !== node else {
       append(value)
       return tail!

From 3191c0998e447bb3c7e55dcdcac969d3ccba2a53 Mon Sep 17 00:00:00 2001
From: yanqizhao <zhaoyanqi703@hellobike.com>
Date: Thu, 28 Apr 2022 20:02:42 +0800
Subject: [PATCH 3/3] fix: fix the wrong return value of
 copyNodes(returningCopyOf:) when  isKnownUniquelyReferenced is true

---
 .../projects/finished/LinkedList.playground/Contents.swift   | 5 +++++
 .../finished/LinkedList.playground/Sources/LinkedList.swift  | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
index fce6265..82817f6 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
@@ -140,4 +140,9 @@ example(of: "linked list cow") {
     }
     print("List2: \(list2)")
 
+    print("Removing middle node on list2")
+    if let node3 = list2.node(at: 1) {
+      list2.remove(after: node3)
+    }
+    print("List2: \(list2)")
 }
diff --git a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
index 2c9439d..0e49f2b 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
@@ -117,7 +117,7 @@ public struct LinkedList<Value> {
   
   private mutating func copyNodes(returningCopyOf node: Node<Value>?) -> Node<Value>? {
     guard !isKnownUniquelyReferenced(&head) else {
-      return nil
+      return node
     }
     guard var oldNode = head else {
       return nil