feat: add swift implementation to lcof problem: No.68.2 (#2964)

Author: klever34

lcof/面试题68 - II. 二叉树的最近公共祖先/README.md

@@ -295,6 +295,41 @@ var lowestCommonAncestor = function (root, p, q) {
 };
 ```
 
+#### Swift
+
+```swift
+/* public class TreeNode {
+*     public var val: Int
+*     public var left: TreeNode?
+*     public var right: TreeNode?
+*     public init() { self.val = 0; self.left = nil; self.right = nil; }
+*     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+*     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+*         self.val = val
+*         self.left = left
+*         self.right = right
+*     }
+* }
+*/
+
+class Solution {
+    func lowestCommonAncestor(_ root: TreeNode?, _ p: TreeNode, _ q: TreeNode) -> TreeNode? {
+        if root == nil || root === p || root === q {
+            return root
+        }
+
+        let left = lowestCommonAncestor(root?.left, p, q)
+        let right = lowestCommonAncestor(root?.right, p, q)
+
+        if let _ = left, let _ = right {
+            return root
+        }
+
+        return left ?? right
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof/面试题68 - II. 二叉树的最近公共祖先/Solution.swift

@@ -0,0 +1,30 @@
+/* public class TreeNode {
+*     public var val: Int
+*     public var left: TreeNode?
+*     public var right: TreeNode?
+*     public init() { self.val = 0; self.left = nil; self.right = nil; }
+*     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+*     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+*         self.val = val
+*         self.left = left
+*         self.right = right
+*     }
+* }
+*/
+
+class Solution {
+    func lowestCommonAncestor(_ root: TreeNode?, _ p: TreeNode, _ q: TreeNode) -> TreeNode? {
+        if root == nil || root === p || root === q {
+            return root
+        }
+
+        let left = lowestCommonAncestor(root?.left, p, q)
+        let right = lowestCommonAncestor(root?.right, p, q)
+
+        if let _ = left, let _ = right {
+            return root
+        }
+
+        return left ?? right
+    }
+}