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A-LevelComputer ScienceData types and structures9618/32 · May/June 2025 · Q116 Marks

A linked list of nodes is used to store an ordered list of strings. Each node consists of the data, a left pointer and a right pointer. Left pointer Data Right pointer [Box: Pp] The linked list will be organised as a binary tree. 0 is used to represent a null pointer. Complete the binary tree, including null pointers, to show how the data will be organised after the following strings have been added: Aa, Mm, Ss, Xx Root pointer [Incomplete binary tree diagram with Gg, Kk, Pp, Rr nodes and spaces for others]

  1. (a)A linked list of nodes is used to store an ordered list of strings. Each node consists of the data, a left pointer and a right pointer. Left pointer Data Right pointer [Box: Pp] The linked list will be organised as a binary tree. 0 is used to represent a null pointer. Complete the binary tree, including null pointers, to show how the data will be organised after the following strings have been added: Aa, Mm, Ss, Xx Root pointer [Incomplete binary tree diagram with Gg, Kk, Pp, Rr nodes and spaces for others][4]
  2. (b)A binary tree can be used to implement recursion. Identify one feature of an algorithm that makes it beneficial to use recursion. Give one example of an application that could use a recursive algorithm. Feature Example[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

  1. MP1 Any two nodes added correctly with correct data (Aa, Mm, Ss, Xx)
  2. MP2 Remaining two nodes added with correct data (Aa, Mm, Ss, Xx) and all nodes with connecting arrows starting from correct pointer boxes
  3. MP3 Correct null pointers (0) added throughout
  4. MP4 with no entries in other pointer boxes and all nodes correctly positioned and connected.
  5. Recursion is beneficial for algorithms when a problem naturally breaks down into smaller versions of itself.
  6. such as calculating a factorial / mathematical series / Fibonacci / compound interest / tree traversal / evaluation of RPN expressions.

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About this question

Topic
Data types and structures, A-Level Computer Science (syllabus 9618). Structured question, 6 marks.
Source
A-Level Computer Science, May/June 2025 Paper 3 Variant 2, question 11.

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