Lesson 4.3.2.1

4.3.2.1 Pre-order, post-order and in-order traversal Quiz: AQA Computer Science, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 4.3.2.1, Pre-order, post-order and in-order traversal: 20 multiple choice questions for the AQA Computer Science (7517), Unit 3: Fundamentals of algorithms, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. Which traversal visits the root first, then the left subtree, then the right subtree?

    • Post-order
    • Level-order
    • In-order
    • Pre-order

  2. Which traversal of a binary search tree outputs values in ascending order?

    • Pre-order
    • Breadth-first
    • Post-order
    • In-order

  3. Which tree traversal produces Reverse Polish Notation from an expression tree?

    • In-order
    • Breadth-first
    • Pre-order
    • Post-order

  4. When is the root node visited during a post-order tree traversal?

    • In the middle
    • Last
    • Second
    • First

  5. Which traversal is used when copying a tree?

    • Inverse-order
    • Post-order
    • In-order
    • Pre-order

  6. In-order traversal visits nodes in which sequence?

    • Left, root, right
    • Left, right, root
    • Right, root, left
    • Root, left, right

  7. Post-order traversal visits nodes in which sequence?

    • Root, left, right
    • Right, left, root
    • Left, right, root
    • Left, root, right

  8. An expression tree has root '+', left child '*' with children 'a' and 'b', and right child 'c'. What is the pre-order output?

    • +c*ab
    • +*abc
    • abc*+
    • a*b+c

  9. Using the same expression tree (root '+', left '*' with children 'a' and 'b', right 'c'), what is the in-order output?

    • ab*c+
    • c+ab*
    • a*b+c
    • +*abc

  10. Using the same expression tree, what is the post-order output?

    • a*b+c
    • +*abc
    • cab*+
    • ab*c+

  11. A binary search tree is built by inserting 5, 3, 8, 1 and 4 in that order. What is its in-order output?

    • 8, 5, 4, 3, 1
    • 1, 3, 4, 5, 8
    • 1, 4, 3, 8, 5
    • 5, 3, 1, 4, 8

  12. For the same binary search tree (root 5, left 3 with children 1 and 4, right 8), what is the pre-order output?

    • 1, 3, 4, 5, 8
    • 5, 3, 1, 4, 8
    • 5, 8, 3, 4, 1
    • 1, 4, 3, 8, 5

  13. For the same binary search tree, what is the post-order output?

    • 1, 4, 3, 8, 5
    • 1, 3, 4, 8, 5
    • 8, 4, 1, 3, 5
    • 5, 3, 1, 4, 8

  14. Which tree traversal outputs the nodes of a binary search tree in ascending order?

    • Level-order
    • Post-order
    • In-order
    • Pre-order

  15. Infix to postfix conversion of an expression tree uses which traversal?

    • In-order
    • Pre-order
    • Post-order
    • Level-order only

  16. Which traversal is used to empty a tree, as listed in the specification?

    • Breadth-first
    • Pre-order
    • Post-order
    • In-order

  17. A tree has root 4, left child 2 (children 1 and 3), and right child 6 (children 5 and 7). What is the in-order output?

    • 4, 2, 1, 3, 6, 5, 7
    • 1, 3, 2, 5, 7, 6, 4
    • 1, 2, 3, 4, 5, 6, 7
    • 7, 6, 5, 4, 3, 2, 1

  18. For the same tree (root 4, left 2 with children 1 and 3, right 6 with children 5 and 7), what is the pre-order output?

    • 4, 6, 2, 5, 7, 1, 3
    • 4, 2, 1, 3, 6, 5, 7
    • 1, 2, 3, 4, 5, 6, 7
    • 1, 3, 2, 5, 7, 6, 4

  19. For the same tree, what is the post-order output?

    • 1, 2, 3, 4, 5, 6, 7
    • 4, 2, 1, 3, 6, 5, 7
    • 7, 5, 6, 3, 1, 2, 4
    • 1, 3, 2, 5, 7, 6, 4

  20. Which traversal sequence is used when copying the structure of a binary tree?

    • Post-order
    • Level-order
    • In-order
    • Pre-order

All AQA Computer Science quizzes