Sibling Check in Ancestral Tree | Dataford Interview Questions

Given an infinite ancestral tree where every person has two parents (child -> parent links), determine whether two given people are siblings.

Asked in the onsite DSA 2 stage. This is not a normal tree: each node has two parents. Reported follow-ups include determining first cousins and finding the lowest common ancestor.

Input and Output

Implement are_siblings(person1, person2, parents). parents maps each person ID to a list of their two parent IDs. Return True when the two distinct people share at least one immediate parent, otherwise return False. A person absent from parents has no listed parents.

Constraints

Person IDs are hashable values.
Each listed person has exactly two parent IDs.
A person may be absent from parents, in which case no parent links are available.
Only immediate parents determine the result.

Function Signature

def are_siblings(person1, person2, parents):

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