Let \(T\) be a binary search tree with \(15\) nodes. The minimum and maximum…

2017

Let \(T\) be a binary search tree with \(15\) nodes. The minimum and maximum possible heights of \(T\) are:

Note: The height of a tree with a single node is \(0\).

  1. A.

    4 and 15 respectively.

  2. B.

    3 and 14 respectively.

  3. C.

    4 and 14 respectively.

  4. D.

    3 and 15 respectively.

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Correct answer: B

Key idea: relate the number of nodes to tree height.

  • Minimum possible height: A perfect binary tree of height h has 2^(h+1) - 1 nodes. Find the smallest h with 2^(h+1) - 1 ≥ 15. Since 2^4 - 1 = 15, we get h = 3. So the minimum height is 3.

  • Maximum possible height: The worst-case (degenerate) BST is a chain. Its height equals number of nodes minus 1, so height = 15 - 1 = 14.

Conclusion: The minimum possible height is 3 and the maximum possible height is 14.

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