feat: add swift implementation to lcof2 problem: No.047 (doocs#3062)

Author: klever34

lcof2/剑指 Offer II 047. 二叉树剪枝/README.md

@@ -201,6 +201,46 @@ var pruneTree = function (root) {
 };
 ```
 
+#### Swift
+
+```swift
+/* class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init() {
+*         self.val = 0
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+*         self.val = val
+*         self.left = left
+*         self.right = right
+*     }
+* }
+*/
+
+class Solution {
+    func pruneTree(_ root: TreeNode?) -> TreeNode? {
+        guard let root = root else {
+            return nil
+        }
+        root.left = pruneTree(root.left)
+        root.right = pruneTree(root.right)
+        if root.val == 0 && root.left == nil && root.right == nil {
+            return nil
+        }
+        return root
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 047. 二叉树剪枝/Solution.swift

@@ -0,0 +1,35 @@
+/* class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init() {
+*         self.val = 0
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+*     init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+*         self.val = val
+*         self.left = left
+*         self.right = right
+*     }
+* }
+*/
+
+class Solution {
+    func pruneTree(_ root: TreeNode?) -> TreeNode? {
+        guard let root = root else {
+            return nil
+        }
+        root.left = pruneTree(root.left)
+        root.right = pruneTree(root.right)
+        if root.val == 0 && root.left == nil && root.right == nil {
+            return nil
+        }
+        return root
+    }
+}