GCE Computer Science H446/02: Algorithms and programming Advanced GCE Mark Scheme for November 2020

GCE Computer Science H446/02: Algorithms and programming Advanced GCE Mark Scheme for November 2020Oxford Cambridge and RSA Examinations OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of candidates of all ages and abilities. OCR qualifications include AS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new specifications to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support, which keep pace with the changing needs of today’s society. This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which marks were awarded by examiners. It does not indicate the details of the discussions which took place at an examiners’ meeting before marking commenced. All examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes should be read in conjunction with the published question papers and the report on the examination. © OCR 2020H446/02 Mark Scheme November 2020 2 Annotations Annotation Meaning Omission mark Benefit of the doubt Subordinate clause / consequential error Incorrect point Expansion of a point Follow through Not answered question No benefit of doubt given Point being made Repeat Correct point Too vague Zero (big) Blank Page – this annotation must be used on all blank pages within an answer booklet (structured or unstructured) and on each page of an additional object where there is no candidate response.H446/02 Mark Scheme November 2020 Level 1 Level 2 Level 3H446/02 Mark Scheme November 2020 4 Question Answer Marks Guidance 1a 1 mark for definition • Removal of unnecessary detail // Simplification to allow development of a program more easily 1 mark to max 2 for application e.g. • The actual movements are represented by vertices/lines • State of the move is represented by a letter/symbol rather than the actual move position • Tree does not show details about what the moves are 3 AO1.1 (1) AO2.1 (1) AO2.2 (1) Allow other suitable examples that are relevant to the scenario in the question. 1b One node (node A) has more than 2 connections Nodes aren’t ordered (e.g. F is C’s left child) 1 AO2.1 (1) 1c 1 mark for identification • Null pointers 1 AO2.1 (1) 1d 1 mark per bullet • Take A as starting node • Visit B, C and E • Visit D, F, G and H • Visit I and J 4 AO1.2 (2) AO2.2 (2) Allow the reverse ordering from right to left e.g. A; E, C, B; H, G, F, D; J, I 1ei 1 mark per bullet to max 3 • Search the tree to find the location of Node E // by example of search • Replace the content of node E with blank/null/equivalent • Make node A point to the node H • Add node E to the empty node list 3 AO1.2 (3) 1eii 1 mark per bullet to max 3 • Search the tree to find the location of node G // by example of search • Create a new node with value K • Add a pointer from node G to the new node • Make node K point to null/equivalent 3 AO1.2 (3)