CS445 Recitation 7:25pm8:15pm

1
CS445 Recitation725pm-815pm

• Feb 6 8, 2007 (T,H)
• The first test will be Tuesday February 13.
• There will be no recitations during test week.

2
An opportunity

• FYI GoldenGate is opening a small office in
  Pittsburgh which may expand if successful. This
  company definitely has a lot of potential to be a
  good partner for us.
• GoldenGate Software Pre-Interview Meeting
  GoldenGate Software of San Francisco, CA is
  hiring talented software graduates. They have a
  pre-interview meeting on Feb. 12 at 5pm, where
  you will get the chance to meet with GoldenGate's
  top engineering and technology executives. For
  more information, read the flyer on the CS Home
  page. Make sure to you bring your resume.
  Refreshments will be provided.

3
Homework 3

• Problem statement
• In the Euclidean Traveling Salesman Problem (TSP)
  you are given a set of cities (which are points
  in the plane) and are asked to find a shortest
  tour that connects all of them and returns to the
  starting city. The problem is equivalent to many
  important practical problems.
• Greedy Search
• Greedy Search is a simple, yet relatively
  effective. algorithm that starts with a city and
  always adds the city closest to the most recently
  added. Briefly, this can be stated as
• Add the starting city to the tour.
• While there are unvisited cities
• Find the city closest to the last visited city.
• Add it to the tour.
• Add the starting city to the tour.

4
Homework 3
1
2
3
4
5
7
8
0
6
a
1
b
2
c
d
e
3
f
4
5
5
Homework 3
1
2
3
4
5
7
8
0
6
a
1
b
2
c
d
e
3
f
4
5
Start from a, the tour is a, c, f, d, b, e, a
6
Homework 3
1
2
3
4
5
7
8
0
6
a
1
b
2
c
d
e
3
f
4
5
Start from b, a tour is b, d, e, f, c, a, b
7
Homework 3
1
2
3
4
5
7
8
0
6
a
1
b
2
c
d
e
3
f
4
5
Start from b, another tour is b, e, d, f, c, a,
b
8
Homework 3

• First, you will implement the class
  MyArrayListltTgt with the following methods
• public MyArrayList() creates a new list.
• public T add(T element) adds an element at the
  end and returns it.
• public T add(int index, T element) adds an
  element at index and returns it.
• public T get(int index) returns the element at
  index.
• public T remove(int index) removes the element at
  index.
• public boolean contains(T element) looks for
  element.
• public int size() returns the size of the list.
• public String toString() returns a string
  suitable for printing.
• Your class should perform similarly to Java's
  ArrayListltTgt class. BUT YOU ARE NOT ALLOWED TO
  DIRECTLY OR IN DIRECTLY USE Java's ArrayListltTgt
  class. In particular, there should be no
  arbitrary limit on the size of the list, and
  retrieval with get() should require only a
  constant amount of time.

9
Homework 3

• Two examples earn no or few points

import java.util.ArrayList
//
Absolutely no point public class MyArrayListltTgt
extends ArrayListltTgt
import java.util.ArrayList public class
MyArrayListltTgt private ArrayListltTgt elements
public MyArrayList() elements new
ArrayListltTgt() public T add(T element)
elements.add(element) return element public
T add(int index, T element) elements.add(index,
element) return element public T remove(int
index) T element elements.get(index)
elements.remove(index) return element public
String toString()
// MAYBE some partial points
for this method String result "" for
(int i 0 i lt elements.size() i) result
elements.get(i) " " return result

10
Homework 3

• Second, you will implement the City class which
  must have an appropriate toString() method.

11
Homework 3

• Third, you will implement the TravelingSalesman
  class with the following methods
• public TravelingSalesman() constructs a new TSP.
• public void addCity(String n, int x, int y) adds
  a city to the TSP.
• public MyArrayListltCitygt tour(String c) greedily
  finds a tour.
• In addition, you should probably implement a few
  auxiliary classes to help solve this problem.

12
Homework 3

• Documentation
• All of your files should include a header with
  your name and email address.
• Your code should be cleanly designed, logically
  organized, and easy to follow. Document any
  tricky or subtle parts of the code.
• You also need to include the files
• README contains brief documentation in
  plain-text.
• DemonstrateTSP.java demonstrates your code.
• You can use Dr. Aroniss files TSP-README and
  DemonstrateTSP.java (in the miscellaneous
  directory) as examples.
• If you cannot finish this project, document what
  you have in the README file and drive any parts
  that work in DemonstrateTSP.java. Make it easy
  for us to award partial credit!

13
Homework 3

• Bundle your files with tar or zip and submit it
  to
• /afs/cs.pitt.edu/public/incoming/aronis/cs445/home
  work-3/xxx.tar
• or
• /afs/cs.pitt.edu/public/incoming/aronis/cs445/home
  work-3/xxx.zip
• where XXX indicates how you bundled your
  files.
• How to use tar
• Create a tar file
• tar -cf ShuyiShao.tar README MyArrayList.java
  City.java DemonstrateTSP.java
• List all files in ShuyiShao.tar verbosely
• tar tvf ShuyiShao.tar
• Extract all files from ShuyiShao.tar
• tar xf ShuyiShao.tar
• This project is due Friday February 16 at
  1159pm.

14
Hw2 grading policies

• No significant problems 10 points
• Minor problems 8 points
• Major problems 6 points
• Doesn't work 4 points
• Handed something in 2 points

15
HW 2 Solution

• Good for recursion