Python hacks
\nclass FindElements(object):\n    def __init__(self, root):\n        def v(r, x):\n            return r and {x} | v(r.left, 2*x+1) | v(r.right, 2*x+2) or set()
```\nclass FindElements(object):\n    def __init__(self, root):\n        def v(r, x):\n            return r and {x} | v(r.left, 2*x+1) | v(r.right, 2*x+2) or set()\n        self.find = v(root, 0).__contains__\n```\n\nAnother, based on [this one](https://leetcode.com/problems/find-elements-in-a-contaminated-binary-tree/discuss/431229/Python-Special-Way-for-find()-without-HashSet-O(1)-Space-O(logn)-Time/394342):\n```\nclass FindElements(object):\n    def __init__(self, r):\n        self.find = lambda t: reduce(lambda n, b: n and (n.left, n.right)[int(b)], bin(t+1)[3:], r)\n```\n
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