CMSC 131: Chapter 30 (Supplement)
CMSC 131: Chapter 30 (Supplement)
Sorting
Sorting
Sorting and Searching
Sorting and Searching
Sorting: Given a list of items from any ordered domain (integers, doubles, Strings,
Dates, …) permute (rearrange) the elements so they are in increasing order.
Searching: Given a list of items and given a designated query item q, determine
whether q appears in the list, and if so, then where.
Sorting and Searching: are two of the most fundamental tasks in all of computer
science.
– Although these may seem pretty simple, there are many different ways to solve these
problems.
– These approaches are quite different in terms of complexity and efficiency.
– There is a 722 page book (by D. E. Knuth) devoted to just these two topics alone!
Note: We will talk only about Sorting (one type of Sort: Selection Sort). You will see
Search in CMSC 132.
Selection Sort
Selection Sort
Selection Sort: one of the simplest sorting algorithms known. (Recall: an
algorithm is a method of solving a problem.)
Input Argument: Let a denote the array to be sorted. We assume only that the
elements of a are from any class that implements the Comparable interface,
that is, it defines a public method:
int compareTo( Object obj )
This compares the current object to object obj. It returns:
< 0 if this < obj
== 0 if this == obj
> 0 if this > obj
Examples of Objects that implement Comparable:
– All the numeric wrappers (Integer, Double, Float, etc.)
–String
– Any class of yours, for which you define compareTo( ).
