Which of the following statements is false?

1998

Which of the following statements is false?

  1. A.

    A tree with n nodes has n - 1 edges.

  2. B.

    A labeled rooted binary tree can be uniquely constructed from its preorder and postorder traversal results.

  3. C.

    A complete binary tree with n internal nodes has n + 1 leaves.

  4. D.

    The maximum number of nodes in a binary tree of height h is 2^(h + 1) - 1.

Attempted by 46 students.

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Correct answer: B

Option B is false. A general labeled rooted binary tree cannot be uniquely reconstructed from only preorder and postorder traversals. For example, preorder A, B and postorder B, A can represent a tree where B is the left child of A, or a tree where B is the right child of A. Both give the same preorder and postorder sequences.

Option A is true because any tree with n nodes has n - 1 edges. Option C is true under the complete/full binary tree convention used in this question: if each internal node has two children, then leaves = internal nodes + 1. Option D is true because the maximum number of nodes in a binary tree of height h is 1 + 2 + ... + 2^h = 2^(h + 1) - 1. Hence, option B is the false statement.

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