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Convert the tree to a general graph, and do a breadth-first search. Alternatively, find the closest leaf for every node on the path from root to target.
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Yes, variations of tree-to-graph transformation and BFS traversal are common in technical interviews. Problems like this test understanding of tree traversal, graph modeling, and shortest-path intuition, which are important concepts in FAANG-level interviews.
A parent map allows traversal from a node back to its parent, effectively turning the tree into a bidirectional graph. This is important because the closest leaf might exist outside the target node’s subtree. With parent links, BFS can explore all possible directions.
The optimal approach converts the tree into an undirected graph by storing parent references. After that, a BFS is performed starting from the target node to find the nearest leaf. Because BFS explores nodes level by level, the first leaf encountered is the closest one.
A queue is essential for the BFS traversal that finds the nearest leaf. Additionally, a hash map is typically used to store parent relationships, and a hash set helps track visited nodes to prevent revisiting them.