Structured Problem Solving

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Structured Problem Solving

• Data Structures 1

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What we shall do in this part of the course

• Concept of a data structure
• Examples of data structures
• records
• arrays
• sequences (lists, queues, stacks)

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An example of a data structure

• Set of record cards containing quiz league details

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Where is the structure in this?

• The information is organised in a logical way
• One card for each team
• Same 4 pieces of information for each team
• Each piece of information made up of words and
  numbers
• Each word made up of letters
• Each number made up of digits

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A question

• The simplest level of data structure in the
  English Football League is the player. What
  levels of data structure can you identify?
• divisions forming the Football League
• teams forming a division
• players forming a team
• individual players

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Important point

• There is a difference between a data structure
  and the data stored in it
• In the quiz team example the data structure
• Box for the cards
• Blank cards with lines drawn in to hold the 4
  items of information

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Data types
Black Arrows
The Red Lion
West Road, Bolton
0204 3521345
Monday

• Each part of the card holds a particular type of
  information

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This modules data structures

• records
• arrays
• sequences (lists, queues, stacks)

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Records Chapter 3

• A record is a collection of different data types
• All other data structures we shall meet on this
  module are collections of items of the same data
  type

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Record structure

• Each piece of information is a field
• For each field we need to know
• its identifier or label
• the type of information it can contain

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Quiz team record structure

• No two fields can have the same label
• Fields do not have to be text

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• Text fields name, nationality, date of birth,
  sex, ID number
• Image field
• Could also have, for example,
• audio field(voice print)
• fingerprint field

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Representing a record as a row of fields
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Arrays and Tables Chapter 4

• An array consists of a fixed number of data
  items.
• Each item is known as an element
• Each element is of the same type
• Each element is associated with a unique number
  called an index

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Array example

• Index range is 1..4
• Each element is a name

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Identifying an array element

• Ford is Manufacturers1
• Volkswagen is Manufacturers2

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Describing an array completely

• The index for the array Manufacturers lies in the
  range 1..4
• The elements are of type Name.

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Quick question

• What is the value of Manufacturers3 ?

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Another example

• What are the contents of the element in the array
  PlayOffTeams which has index 3 ?
• What is the value of PlayOffTeams2 ?

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Example

• Describe completely the structure of the array
  PlayOffTeams.

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Example

• The index for the array PlayOffTeams lies in the
  range 1..4
• The elements are of type Name

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Multi-dimensional arrays

• How do we store a table like this?

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Multi-dimensional arrays

• Use two index numbers
• First identifies the item number
• Second identifies which shop

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Multi-dimensional arrays

• E.g. 37 is Prices2,3
• What price is stored in Prices1,4?
• 61

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Multi-dimensional arrays

• Description of Prices array in a data table

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4 dimension array example

• Seat bookings
• The first index number is in range 1..30 and
  denotes the seat number
• The second index number is in range 1..20 and
  denotes the row number
• The third index number is in range 1..3 and
  denotes the performance number
• The fourth index number is in range 19..23 and
  denotes the date of the performance in January.
• What does Bookings5,7,3,21 represent?
• Seat 5 on 7 row 7 at 3rd performance on 21st
  January