From 7b13520a5d41b981d5c885456f575d678a17a5f8 Mon Sep 17 00:00:00 2001
From: Lanre Adedara <lanre.adedara@shara.co>
Date: Thu, 25 Apr 2024 09:22:43 +0100
Subject: [PATCH 1/4] Swift Implementation for LCCI 04.10

---
 lcci/04.10.Check SubTree/README.md      | 30 +++++++++++++++++++++++++
 lcci/04.10.Check SubTree/README_EN.md   | 30 +++++++++++++++++++++++++
 lcci/04.10.Check SubTree/Solution.swift | 27 ++++++++++++++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 lcci/04.10.Check SubTree/Solution.swift

diff --git a/lcci/04.10.Check SubTree/README.md b/lcci/04.10.Check SubTree/README.md
index fe52620d24a15..78466e6d8d9bc 100644
--- a/lcci/04.10.Check SubTree/README.md	
+++ b/lcci/04.10.Check SubTree/README.md	
@@ -201,6 +201,36 @@ impl Solution {
 }
 ```
 
+```swift
+/* class TreeNode {
+*    var val: Int
+*    var left: TreeNode?
+*    var right: TreeNode?
+*    
+*    init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
+*        self.val = val
+*        self.left = left
+*        self.right = right
+*    }
+* } 
+*/
+
+class Solution {
+    func checkSubTree(_ t1: TreeNode?, _ t2: TreeNode?) -> Bool {
+        if t2 == nil {
+            return true
+        }
+        if t1 == nil {
+            return false
+        }
+        if t1!.val == t2!.val {
+            return checkSubTree(t1!.left, t2!.left) && checkSubTree(t1!.right, t2!.right)
+        }
+        return checkSubTree(t1!.left, t2) || checkSubTree(t1!.right, t2)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->
diff --git a/lcci/04.10.Check SubTree/README_EN.md b/lcci/04.10.Check SubTree/README_EN.md
index b1435c469cd46..d726af3e3dc63 100644
--- a/lcci/04.10.Check SubTree/README_EN.md	
+++ b/lcci/04.10.Check SubTree/README_EN.md	
@@ -208,6 +208,36 @@ impl Solution {
 }
 ```
 
+```swift
+/* class TreeNode {
+*    var val: Int
+*    var left: TreeNode?
+*    var right: TreeNode?
+*    
+*    init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
+*        self.val = val
+*        self.left = left
+*        self.right = right
+*    }
+* } 
+*/
+
+class Solution {
+    func checkSubTree(_ t1: TreeNode?, _ t2: TreeNode?) -> Bool {
+        if t2 == nil {
+            return true
+        }
+        if t1 == nil {
+            return false
+        }
+        if t1!.val == t2!.val {
+            return checkSubTree(t1!.left, t2!.left) && checkSubTree(t1!.right, t2!.right)
+        }
+        return checkSubTree(t1!.left, t2) || checkSubTree(t1!.right, t2)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->
diff --git a/lcci/04.10.Check SubTree/Solution.swift b/lcci/04.10.Check SubTree/Solution.swift
new file mode 100644
index 0000000000000..70a54eb3b1965
--- /dev/null
+++ b/lcci/04.10.Check SubTree/Solution.swift	
@@ -0,0 +1,27 @@
+/* class TreeNode {
+*    var val: Int
+*    var left: TreeNode?
+*    var right: TreeNode?
+*    
+*    init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
+*        self.val = val
+*        self.left = left
+*        self.right = right
+*    }
+* } 
+*/
+
+class Solution {
+    func checkSubTree(_ t1: TreeNode?, _ t2: TreeNode?) -> Bool {
+        if t2 == nil {
+            return true
+        }
+        if t1 == nil {
+            return false
+        }
+        if t1!.val == t2!.val {
+            return checkSubTree(t1!.left, t2!.left) && checkSubTree(t1!.right, t2!.right)
+        }
+        return checkSubTree(t1!.left, t2) || checkSubTree(t1!.right, t2)
+    }
+}
\ No newline at end of file

From 561a9b96a6482a38d360995f32cbc65574d64bbc Mon Sep 17 00:00:00 2001
From: klever34 <klever34@users.noreply.github.com>
Date: Thu, 25 Apr 2024 08:33:52 +0000
Subject: [PATCH 2/4] style: format code and docs with prettier

---
 lcci/04.10.Check SubTree/README.md    | 4 ++--
 lcci/04.10.Check SubTree/README_EN.md | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/lcci/04.10.Check SubTree/README.md b/lcci/04.10.Check SubTree/README.md
index 78466e6d8d9bc..01724ce5d0a3f 100644
--- a/lcci/04.10.Check SubTree/README.md	
+++ b/lcci/04.10.Check SubTree/README.md	
@@ -206,13 +206,13 @@ impl Solution {
 *    var val: Int
 *    var left: TreeNode?
 *    var right: TreeNode?
-*    
+*
 *    init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
 *        self.val = val
 *        self.left = left
 *        self.right = right
 *    }
-* } 
+* }
 */
 
 class Solution {
diff --git a/lcci/04.10.Check SubTree/README_EN.md b/lcci/04.10.Check SubTree/README_EN.md
index d726af3e3dc63..e163a2f343aab 100644
--- a/lcci/04.10.Check SubTree/README_EN.md	
+++ b/lcci/04.10.Check SubTree/README_EN.md	
@@ -213,13 +213,13 @@ impl Solution {
 *    var val: Int
 *    var left: TreeNode?
 *    var right: TreeNode?
-*    
+*
 *    init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
 *        self.val = val
 *        self.left = left
 *        self.right = right
 *    }
-* } 
+* }
 */
 
 class Solution {

From 8f551600dc16823db568dcd5b2e4773043b91068 Mon Sep 17 00:00:00 2001
From: Lanre Adedara <lanre.adedara@shara.co>
Date: Thu, 25 Apr 2024 13:37:34 +0100
Subject: [PATCH 3/4] code logic update

---
 lcci/04.10.Check SubTree/README.md      | 17 +++++++++++++++--
 lcci/04.10.Check SubTree/README_EN.md   | 17 +++++++++++++++--
 lcci/04.10.Check SubTree/Solution.swift | 17 +++++++++++++++--
 3 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/lcci/04.10.Check SubTree/README.md b/lcci/04.10.Check SubTree/README.md
index 01724ce5d0a3f..9eb4384eab3bf 100644
--- a/lcci/04.10.Check SubTree/README.md	
+++ b/lcci/04.10.Check SubTree/README.md	
@@ -223,11 +223,24 @@ class Solution {
         if t1 == nil {
             return false
         }
-        if t1!.val == t2!.val {
-            return checkSubTree(t1!.left, t2!.left) && checkSubTree(t1!.right, t2!.right)
+        if isSameTree(t1, t2) {
+            return true
         }
         return checkSubTree(t1!.left, t2) || checkSubTree(t1!.right, t2)
     }
+
+    private func isSameTree(_ t1: TreeNode?, _ t2: TreeNode?) -> Bool {
+        if t1 == nil && t2 == nil {
+            return true
+        }
+        if t1 == nil || t2 == nil {
+            return false
+        }
+        if t1!.val != t2!.val {
+            return false
+        }
+        return isSameTree(t1!.left, t2!.left) && isSameTree(t1!.right, t2!.right)
+    }
 }
 ```
 
diff --git a/lcci/04.10.Check SubTree/README_EN.md b/lcci/04.10.Check SubTree/README_EN.md
index e163a2f343aab..ca16b4debbbde 100644
--- a/lcci/04.10.Check SubTree/README_EN.md	
+++ b/lcci/04.10.Check SubTree/README_EN.md	
@@ -230,11 +230,24 @@ class Solution {
         if t1 == nil {
             return false
         }
-        if t1!.val == t2!.val {
-            return checkSubTree(t1!.left, t2!.left) && checkSubTree(t1!.right, t2!.right)
+        if isSameTree(t1, t2) {
+            return true
         }
         return checkSubTree(t1!.left, t2) || checkSubTree(t1!.right, t2)
     }
+
+    private func isSameTree(_ t1: TreeNode?, _ t2: TreeNode?) -> Bool {
+        if t1 == nil && t2 == nil {
+            return true
+        }
+        if t1 == nil || t2 == nil {
+            return false
+        }
+        if t1!.val != t2!.val {
+            return false
+        }
+        return isSameTree(t1!.left, t2!.left) && isSameTree(t1!.right, t2!.right)
+    }
 }
 ```
 
diff --git a/lcci/04.10.Check SubTree/Solution.swift b/lcci/04.10.Check SubTree/Solution.swift
index 70a54eb3b1965..5cb011e335bd1 100644
--- a/lcci/04.10.Check SubTree/Solution.swift	
+++ b/lcci/04.10.Check SubTree/Solution.swift	
@@ -19,9 +19,22 @@ class Solution {
         if t1 == nil {
             return false
         }
-        if t1!.val == t2!.val {
-            return checkSubTree(t1!.left, t2!.left) && checkSubTree(t1!.right, t2!.right)
+        if isSameTree(t1, t2) {
+            return true
         }
         return checkSubTree(t1!.left, t2) || checkSubTree(t1!.right, t2)
     }
+
+    private func isSameTree(_ t1: TreeNode?, _ t2: TreeNode?) -> Bool {
+        if t1 == nil && t2 == nil {
+            return true
+        }
+        if t1 == nil || t2 == nil {
+            return false
+        }
+        if t1!.val != t2!.val {
+            return false
+        }
+        return isSameTree(t1!.left, t2!.left) && isSameTree(t1!.right, t2!.right)
+    }
 }
\ No newline at end of file

From 9276667d4ed505c75d2b140c50c252a37fb3e94f Mon Sep 17 00:00:00 2001
From: Libin YANG <contact@yanglibin.info>
Date: Thu, 25 Apr 2024 20:57:41 +0800
Subject: [PATCH 4/4] Update README_EN.md

---
 lcci/04.10.Check SubTree/README_EN.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lcci/04.10.Check SubTree/README_EN.md b/lcci/04.10.Check SubTree/README_EN.md
index 58d66e46703c6..b8b0c534015df 100644
--- a/lcci/04.10.Check SubTree/README_EN.md	
+++ b/lcci/04.10.Check SubTree/README_EN.md	
@@ -42,7 +42,7 @@ First, we check if $t_2$ is null. If it is, then $t_2$ is definitely a subtree o
 
 Otherwise, we check if $t_1$ is null. If it is, then $t_2$ is definitely not a subtree of $t_1$, so we return `false`.
 
-Next, we check if $t_1$ and $t_2$ are equal. If they are, then $t_2$ is a subtree of $t_1$, so we return `true`. Otherwise, we recursively check if $t_1$'s left subtree is equal to $t_2$, and if $t_1$'s right subtree is equal to $t_2$. If either is `true`, then $t_2$ is a subtree of $t_1`, so we return `true`.
+Next, we check if $t_1$ and $t_2$ are equal. If they are, then $t_2$ is a subtree of $t_1$, so we return `true`. Otherwise, we recursively check if $t_1$'s left subtree is equal to $t_2$, and if $t_1$'s right subtree is equal to $t_2$. If either is `true`, then $t_2$ is a subtree of $t_1$, so we return `true`.
 
 The time complexity is $O(n^2)$, and the space complexity is $O(n)$. Where $n$ is the number of nodes in $t_1$.