3.2 Data Abstraction (list)
1. Exam Points
Benefits of using lists.
- Lists often allow their
size to be easily updated to hold as many data values as needed. (append, insert, remove etc.)
- Easier to apply the
same computation to every element.
Index of list elements start from 1, ends at size - 1.Indexex of String characters start from 1. (Ex. ”abc”, the index of a is 1)Predict the result after some operations on a list.
2. Knowledge Points
(1) list (列表)
A list is an ordered sequence of elements(元素).- Format: [value1, value2, value3, ...]
- Example:
- An
element is an individual value in a list that is assigned a unique index.
- The
valid index of a list is of range: 1 to size - 1
- Here value1 is the first element, value2 is the second element, value3 is the third element, and so on.
- An index is a common method for referencing the elements in a
list or string using natural numbers (1,2,3,…).
- Example:
- [10, 20, 30, 40, 50, 60] : index of 10 is 1, index of 60 is 6.
- Annabelle: index of A is 1, index of b is 5.
- Data abstractions reduce complexity in programs by
giving a collection of data a name without referencing the specific details of the representation.
- Data abstractions can be created using lists.
(2) Create a list
Syntax:
- Example:
Create a list: aList ← [10, 20, 30, 40]Create an empty list: bList ← []Assign a copy of aList to bList: bList ← aList
3. Exercises
