Swift🔥1liner
One-Liner (accepted answer)\n\nclass Solution {\n    func postorder(_ root: Node?) -> [Int] {\n    \troot == nil ? [] : root!.children.flatMap(postorder) + [roo
**One-Liner (accepted answer)**\n```\nclass Solution {\n    func postorder(_ root: Node?) -> [Int] {\n    \troot == nil ? [] : root!.children.flatMap(postorder) + [root!.val]\n    }\n}\n```
['Swift']