Suppose the numbers 7, 5, 1, 8, 3, 6, 0, 9, 4, 2 are inserted in that order…

2003

Suppose the numbers 7, 5, 1, 8, 3, 6, 0, 9, 4, 2 are inserted in that order into an initially empty binary search tree. The binary search tree uses the usual ordering on natural numbers. What is the in-order traversal sequence of the resultant tree ?

  1. A.

    7 5 1 0 3 2 4 6 8 9

  2. B.

    0 2 4 3 1 6 5 9 8 7

  3. C.

    0 1 2 3 4 5 6 7 8 9

  4. D.

    9 8 6 4 2 3 0 1 5 7

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Correct answer: C

Key insight: in-order traversal of a binary search tree visits the left subtree first, then the node, then the right subtree.

  • Because the tree is a binary search tree, an in-order traversal always produces the node values in ascending (sorted) order.

  • All integers from 0 through 9 are present in the tree after the given insertions, so the sorted ascending sequence is the consecutive numbers 0 through 9.

Therefore the in-order traversal sequence is: 0 1 2 3 4 5 6 7 8 9

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