solve problem

Author: delight010

invert-binary-tree/delight010.swift

@@ -0,0 +1,41 @@
+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 {
+    // Time O(n)
+    // Space O(n)
+    func invertTree(_ root: TreeNode?) -> TreeNode? {
+        guard let root = root else {
+            return nil
+        }
+
+        var queue: [TreeNode] = [root]
+
+        while queue.isEmpty == false {
+            let current = queue.removeFirst()
+
+            if let left = current.left {
+                queue.append(left)
+            }
+
+            if let right = current.right {
+                queue.append(right)
+            }
+
+            (current.left, current.right) = (current.right, current.left)
+        }
+
+        return root
+    }
+}
+