Is O(1) achievable? The add_child function asks for a target of O(1), a tree data structure wouldn't be able to achieve this, finding from root the parent to link the child would be O(n). A set would meet O(1) but would have trouble with get_primogeniture_order which asks for O(n) and going through the set several times to find the eldest child of the eldest child of the... and so on would be O(n^2) because if it was held in n + n-1 + n-2 ... +1 that solves to O(n^2). So far I have opted for a hashmap, which under most circumstances is O(1) under the very rare occurrence that everything hashes to the same key, then it would have worst case O(n). Am I missing a data structure that could achieve all target time complexities or does target time complexity allow for hashtables that would be just off? Kind Regards Bill