Day 20: Other Collection Types

Learning Objectives

• AAP-1.C: Represent a list or string using a variable.
• AAP-1.D: For data abstraction: Develop data abstraction using lists to store multiple elements.

Essential Questions

• What other data structures can we use to organize and store collections of data?
• How do we choose the appropriate collection type for different problems?

Materials Needed

• Presentation slides on collection types
• Programming environment
• Collection type comparison worksheet
• Problem scenarios for different collection types
• Exit ticket templates

Vocabulary

• Collection
• Dictionary
• Key-value pair
• Set
• Hash table
• Map
• Associative array
• Data structure
• Lookup

Procedure (50 minutes)

Opening (8 minutes)

1. Review and Connection (3 minutes)

   • Review 2D lists and nested loops from previous lesson
   • Connect to today's focus on other ways to organize collections of data

2. Warm-up Activity (5 minutes)

   • Present a problem that's awkward to solve with lists (e.g., storing student grades by name)
   • Ask students how they might approach this with what they know so far
   • Discuss limitations of lists for certain types of data organization

Main Activities (32 minutes)

3. Lecture: Other Collection Types (12 minutes)

   • Introduce dictionaries/maps as key-value collections:
     • Structure: mapping keys to values
     • Purpose: fast lookup by key
     • Common uses: name-value associations, property lists
     • Operations: creating, accessing by key, modifying, checking existence
   • Introduce sets as unordered collections of unique elements:
     • Structure: collection with no duplicates
     • Purpose: membership testing, eliminating duplicates
     • Common uses: unique items, set operations
     • Operations: adding, removing, checking membership
   • Compare different collection types:
     • Lists: ordered collections, access by position
     • Dictionaries: key-value pairs, access by key
     • Sets: unique elements, membership testing
   • Discuss when to use each collection type:
     • Lists: when order matters, when duplicates are allowed
     • Dictionaries: when you need to look up values by a key
     • Sets: when you only care about membership, not order or count
   • Explain how these collections provide data abstraction

4. Demo: Using Different Collection Types (8 minutes)

   • Walk through examples of different collection types:
     • Creating and using dictionaries for name-value associations
     • Using sets for membership testing and duplicate elimination
     • Converting between collection types
   • Demonstrate solving problems with appropriate collections:
     • Student grade tracker using dictionaries
     • Unique visitor tracker using sets
     • Frequency counter using dictionaries
   • Show how to choose the right collection for different scenarios
   • Highlight the advantages of each collection type

5. Hands-on: Choosing Appropriate Collections for Different Problems (12 minutes)

   • Students work in the programming environment
   • Present several problem scenarios
   • Students determine which collection type is most appropriate for each
   • Have students implement solutions using the chosen collection types
   • Problem ideas:
     • Word frequency counter
     • Contact list manager
     • Inventory system
     • Unique item tracker
   • Encourage students to explain their choice of collection type

Closing (10 minutes)

6. Activity: Converting Between Collection Types (5 minutes)

   • Provide students with data in one collection format
   • Students convert it to another format to solve a specific problem
   • Examples:
     • Converting a list to a set to find unique elements
     • Converting a list to a dictionary for faster lookup
     • Creating a frequency dictionary from a list
   • Share and discuss different approaches
   • Highlight the strengths of each collection type

7. Exit Ticket and Preview (5 minutes)

   • Students create a program that uses appropriate collection types
   • Preview that next class will focus on algorithm efficiency

Assessment

• Formative: Quality of collection type selection and implementation
• Exit Ticket: Appropriateness of collection type choices in the program

Differentiation

For Advanced Students

• Challenge them with more complex problems requiring multiple collection types
• Introduce more specialized collection types (priority queues, etc.)
• Have them implement custom collection behaviors

For Struggling Students

• Provide clearer guidelines for when to use each collection type
• Focus on one new collection type at a time
• Use visual aids to illustrate different collection structures

Homework/Extension

• Complete a worksheet comparing collection types
• Create a program that uses multiple collection types appropriately
• Research how collection types are implemented in different languages

Teacher Notes

• Emphasize that choosing the right data structure is a key programming skill
• Watch for confusion about when to use each collection type
• Make connections to real-world scenarios requiring different organizations
• Consider using physical analogies (dictionary = phone book, set = stamp collection)
• Remind students that the AP exam may ask about appropriate data structures
• This concludes Week 4 of the unit