✅ One Line Solution
(Disclaimer: this is not an example to follow in a real project - it is written for fun and training mostly)\n\n# Code #1\nTime complexity: O(n^2). Space comple
(Disclaimer: this is not an example to follow in a real project - it is written for fun and training mostly)\n\n# Code #1\nTime complexity: $$O(n^2)$$. Space complexity: $$O(n)$$.\n```\nclass Solution:\n    def postorder(self, n: \'Node\') -> List[int]:\n        return n and sum(map(self.postorder,n.children),[])+[n.val] or []\n```\n\n# Code #2\nTime complexity: $$O(n^2)$$. Space complexity: $$O(n)$$.\n```\nclass Solution:\n    def postorder(self, n: \'Node\') -> List[int]:\n        return n and [*chain(*map(self.postorder,n.children)),n.val] or []\n```\n\n# Code #3\nTime complexity: $$O(n)$$. Space complexity: $$O(n)$$.\n```\nclass Solution:\n    def postorder(self, r: \'Node\') -> List[int]:\n        return (f:=lambda n,q=[]:n and [*map(f,n.children),q.append(n.val)] and q)(r)\n```\n\n(Disclaimer 2: code above is just a product of fantasy packed into one line, it is not claimed to be \'true\' oneliners - please, remind about drawbacks only if you know how to make it better)
['Tree', 'Depth-First Search', 'Recursion', 'Python', 'Python3']