1. CS 241 – Computer Programming II Lab Kalpa Gunaratna – kalpa@knoesis.orgkalpa@knoesis.org http://knoesis.wright.edu/researchers/kalpa/

2. Contact  Contact by e-mail  kalpa@knoesis.org kalpa@knoesis.org  Office hours  376 Joshi  Mondays & Wednesday 3:00 pm – 4:00 pm

3. Recursion  Most of the things could be done with loops could be done with recursion as well.  Sometimes recursion is more meaningful when writing code.  Easy to write.  Have to do it correctly and difficult to debug and find errors.  Memory expensive.

4. Simple exampls  Factorial Public int factorial(n) { if(n == 0) { return 1; } else { return n * factorial(n – 1); } Base condition Recursive call

5. In lab  Implement String reversal algorithm using loops.  Then implement the same with recursion.  Hints : you can use string concatenation and cuttong a String using substring(, ).  Show the code and demonstrate. Discuss what you feel about recursion in this example and explain advantages and disadvantages of recursion.

6. Post lab  Calculate all the permutations of a given string using recursion.  For a given String, number of permutations is the factorial of its length.  Break the problem into sub problems and then think how you can construct a recursive answer (assuming you already got solution for the sub problem and proceed to next step).

7. Lab 5 reminders and mistakes  Read the description on what and how to implement. For example, number of balls should be passed to BallPanel constructor.