If you are planning to use JHAVEPOP for your course (or if you just have a question), please contact David Furcy at furcyd@uwosh.edu

JHAVEPOP works great with Firefox, IE7, Safari, Opera, Konqueror, and other browsers.
Among all the browsers we tested, only IE6 had trouble opening dynamically-generated .jnlp files.

Linked list manipulations using JHAVEPOP

Overview

The first 20 exercises on this page are quite short. They will help you master basic pointer and linked list operations. The last 5 programming assignments are more challenging. They will help you become comfortable designing and implementing robust algorithms to manipulate linked lists. Before attempting the exercises, you should take the time to read the following overview of JHAVEPOP carefully.

JHAVEPOP allows you to view the contents of memory as your program executes. When you feed some C++ code as input to JHAVEPOP, it automatically generates a sequence of snapshots. A snapshot depicts the value of all variables in memory after each statement of your program is executed. Therefore, JHAVEPOP makes it easier to test and debug your programs.

How to use JHAVEPOP

Read and understand the exercise fully.
Design your program on paper, then type your code in your favorite text editor.
Paste your code into JHAVEPOP to see the visualization. That is, when your code is ready to test, click on the red button to launch JHAVEPOP (there is one button for each exercise or test case). Wait until the window asking you to paste your code pops up. This window will already contain three or more lines of code. Do not modify these lines (they are there to create the initial setup for the exercise). Simply paste your code below these lines and click OK.

That's it!
The first snapshot will be visible. Under it, you'll find controls to navigate from one snapshot to the next and back. In the right pane, your code will appear highlighted as it gets executed. You can also click the "Info" tab (top right) to find out more about JHAVEPOP.
If you detect an error in your code, use the visualization to help you fix and edit your code in your favorite text editor. When you are ready to test it again, click on the "Setup" tab (top left of the JHAVEPOP window) and then the "Visualize" button (bottom right). You are now ready to paste your new code.
Finally, when you are done working on the exercise, close the JHAVEPOP window by clicking the X in the top-right corner. You will be back on this page and ready to work on another exercise.

How to write your C++ code

JHAVEPOP contains an interpreter for C++. The interpreter has a built-in class called Node with two public data members: info of type 'char', and next of type 'Node *'. This class implements a node in a singly-linked list. Because it focuses on pointer operations for such linked lists, JHAVEPOP's interpreter only supports a sub-set of the C++ language, namely assignment statements, if statements, while and for loops. The following examples illustrate the range of acceptable constructs:

	Construct	Examples
1.	Pointer assignment	n1 = n4->next; n1->next = NULL;
2.	Memory allocation	n3->next->next = new Node('B',NULL);
3.	Data assignment	n1->info = n4->next->info; n1->next->info = 'C';
4.	Memory deallocation	delete n1;
5.	If statement	if (n1==NULL) {...} else {...}
6.	While loop	while ( (n1!=NULL) && (n1->info=='A') ) {...}
7.	For loop	for( n1=n2; n1!=NULL; n1=n1->next ) {...}
8.	Break statement	break;

Keep in mind that ALL blocks within if statements or loops must always be surrounded by braces { }, even when the block contains only one statement. Of course, if statements and loops require boolean expressions, which must be fully parenthesized. Boolean expressions may compare the values of pointer variables, the values of the info data member, or 'char' literals such as 'A', '1', etc. Simple boolean expressions may be combined into compound boolean expressions with the logical operators '&&' or '| |'. However, each boolean expression may NOT contain more than one such operator. That is, a compound boolean expression may combine only two simple boolean expressions.

JHAVEPOP does NOT support:

other data types such as 'int' or 'char' variables
the 'address-of' operator (&)
pointers to pointers
class definitions nor function calls
free-form comments. Instead, all acceptable comments have a prescribed syntax, since they are interpreted by JHAVEPOP as layout directives for the visualization. You should NOT include comments in your code.

Even though JHAVEPOP allows you to declare any number of pointer variables at the top level of your code (but not within a block), you should NOT declare any variable for any of the following exercises and assignments.

Short exercises

Exercises 1 through 11 focus on assignment statements involving pointer variables and pointer-dereferencing operations.
Exercises 12 and 13 focus on simple while loops whose body contains a single assignment statement.
Exercises 14 through 19 can be solved without loops using sequences of assignment statements.
Exercise 20 requires the use of the 'delete' operator.

Exercise

Initial Setup

Final Configuration

Use a single assignment statement to make the pointer p point to the Node with info '2', thus creating a memory leak.

Linked list manipulations using JHAVEPOP

Overview

Short exercises

Programming assignments