feat: add swift implementation to lcp problem: No.44 (#3784)

Author: klever34

lcp/LCP 44. 开幕式焰火/README.md

@@ -159,6 +159,38 @@ func dfs(root *TreeNode) {
 }
 ```
 
+#### Swift
+
+```swift
+/* class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+* }
+*/
+
+class Solution {
+    private var uniqueColors: Set<Int> = []
+    
+    func numColor(_ root: TreeNode?) -> Int {
+        dfs(root)
+        return uniqueColors.count
+    }
+    
+    private func dfs(_ node: TreeNode?) {
+        guard let node = node else { return }
+        uniqueColors.insert(node.val)
+        dfs(node.left)
+        dfs(node.right)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcp/LCP 44. 开幕式焰火/Solution.swift

@@ -0,0 +1,27 @@
+/* class TreeNode {
+*     var val: Int
+*     var left: TreeNode?
+*     var right: TreeNode?
+*     init(_ val: Int) {
+*         self.val = val
+*         self.left = nil
+*         self.right = nil
+*     }
+* }
+*/
+
+class Solution {
+    private var uniqueColors: Set<Int> = []
+    
+    func numColor(_ root: TreeNode?) -> Int {
+        dfs(root)
+        return uniqueColors.count
+    }
+    
+    private func dfs(_ node: TreeNode?) {
+        guard let node = node else { return }
+        uniqueColors.insert(node.val)
+        dfs(node.left)
+        dfs(node.right)
+    }
+}