Class 49: An Introduction to Sorting

Held: Monday, May 2, 2005

Summary: Today we begin to consider the problem of Sorting, putting elements of a collection in order. Sorting is one of the fundamental problems of computing.

Related Pages:

• EBoard.
• Sample Code.

Overview:

• The problem of sorting
• Carefully specifying that problem
• Testing a sorting method

Sorting

• Sorting is the problem of putting the elements of a collection in order.
• There are a variety of ways to express the problem of sorting.
• What kind of collections do we sort?
  • Arrays
  • Vectors
  • Lists
• Do we return a new, sorted, collection, or do we sort "in place" (changing the parameter collection)?
• How do we compare elements?
  • Using the "normal order" for the objects (as governed by the compareTo method)
  • Using an external comparator
• If we use an external comparator, how do we obtain it?
  • As a field of the class that does the sorting
  • As a parameter to the sort method
• For most of our study, we will sort vectors in place with a separate comparator field.

Specifying Sorting

• How do we specify the problem of sorting? We'll look at some of your answers.

Testing

• How would we test a sorter? We'll develop an answer.