Lesson 4.3.4.3

4.3.4.3 Binary tree search Quiz: AQA Computer Science, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.3.4.3, Binary tree search: 20 multiple choice questions for the AQA Computer Science (7517), Unit 3: Fundamentals of algorithms, written with Revision Ninja.

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The 20 questions

  1. What is the time complexity of binary tree search, as stated in the specification?

    • O(n)
    • O(1)
    • O(n log n) on unbalanced trees
    • O(log n)

  2. In a binary search tree, where are values less than a node stored?

    • In a separate list
    • In the left subtree
    • In the parent node only
    • In the right subtree

  3. Which description matches a binary search tree?

    • A tree in which each node has at most two children, with smaller values in the left subtree and larger values in the right subtree
    • A tree in which all values are stored at the leaves only
    • A tree in which each node has exactly three children
    • A linked list of nodes joined in a circle

  4. When searching a binary search tree, at each node which child is followed?

    • Always the right child
    • The parent node
    • Always the left child
    • Left if the target is smaller and right if it is larger

  5. What is the main advantage of binary tree search over linear search when the tree is balanced?

    • It works on unordered data
    • It needs about log n comparisons instead of up to n
    • It uses no memory
    • It sorts the data as it searches

  6. A binary search tree is built by inserting 50, 30, 70, 20, 40, 60 and 80 in that order. How many comparisons are needed to find 60?

    • 2
    • 4
    • 3
    • 1

  7. In the same tree (50, 30, 70, 20, 40, 60, 80), how many comparisons are made searching for 35, which is not present?

    • 2
    • 4
    • 7
    • 3

  8. How many levels does the tree built from 50, 30, 70, 20, 40, 60 and 80 have, counting the root as level 1?

    • 4
    • 7
    • 2
    • 3

  9. Inserting 10, 20 and 30 in that order into an empty binary search tree produces what shape?

    • Two separate trees
    • A chain leaning right, so search becomes linear
    • A balanced tree with 20 at the root, one node on each side
    • A tree with 30 at the root

  10. Why do sorted inserts make binary tree search slow?

    • They cause the tree to be stored as an array
    • They double the number of nodes in the tree, so every search has to check each of them twice over
    • They create a degenerate tree whose height equals the number of items, so search becomes linear
    • They double the number of nodes in the tree

  11. A balanced binary search tree holds 1000 values. Approximately how many comparisons does a search need?

    • 1000
    • 10
    • 500
    • 100

  12. A partial binary search tree has root 50, a right child 70 whose left child is 60. How many comparisons are needed to conclude that 65 is absent?

    • 4
    • 2
    • 5
    • 3

  13. In a binary search tree built from 5, 3, 8, 1 and 4, what is the left child of 3?

    • 1
    • 8
    • 4
    • 5

  14. In the binary search tree built from 5, 3, 8, 1 and 4, how many comparisons are needed to find 4?

    • 4
    • 1
    • 3
    • 2

  15. A perfectly balanced binary search tree has n nodes. Which expression gives its approximate height?

    • n
    • n squared
    • log2(n)
    • n / 2

  16. Why is binary tree search O(log n) on average but O(n) in the worst case?

    • On average the tree is balanced, but the worst case is a degenerate chain whose height equals n
    • Every search visits every node regardless of shape
    • The worst case is always log n because the tree is sorted
    • On average the tree has n/2 levels, and the worst case is constant

  17. Which statement comparing binary search on a sorted array with binary tree search is correct?

    • Binary search is O(n) and binary tree search is O(log n)
    • Both take O(log n) when balanced, but a tree supports insertion and deletion through its pointer structure
    • A binary search tree cannot be searched by value
    • Both always need exactly the same number of comparisons

  18. A binary search tree is built by inserting 8, 3, 10, 1, 6, 14, 4, 7 and 13 in that order. How many comparisons are needed to find 7?

    • 5
    • 3
    • 4
    • 2

  19. For the tree built from 8, 3, 10, 1, 6, 14, 4, 7 and 13, what is the in-order output?

    • 1, 3, 4, 6, 7, 8, 10, 13, 14
    • 8, 3, 1, 6, 4, 7, 10, 14, 13
    • 14, 13, 10, 8, 7, 6, 4, 3, 1
    • 1, 4, 3, 7, 6, 13, 14, 10, 8

  20. What is the main risk of binary tree search on a tree built from already sorted input without rebalancing?

    • The search becomes constant time
    • The search degenerates towards linear time, O(n)
    • The search returns incorrect values
    • The tree cannot store duplicate values

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