1. Recursion Snarf the code for today’s class.

2. Where We Are: Tools and Techniques • Data Structures, like Lists and Maps • Techniques, like Big O analysis • Classes and Inheritance • The essential process of taking a problem and solving it with code All of it happens to be within Java in this course…but these ideas transcend Java

3. Recursion • When a function calls a “clone” of itself • Also, when a Data structure contains a “clone” of itself (but we will save this one for later)

4. What to do • Snarf the code for today’s class if you haven’t already • Go to the quiz section of Sakai • There’s classwork for today there • Go through and try to answer the questions (feel free to take you time, think, and ask a friend) • If you get stuck, run the code and see what’s going on • If you finish it all, start on the BONUS section

5. Two Parts To Every Recursive Function • Base Case if(n == 1) return 1; • Recursive Case return n*recursiveFunction(n-1); The basic idea is to get help solving a problem from coworkers (clones) who work and act like you do. • Ask clone to solve a similar, but smaller/simpler problem • Use the result • Don’t forget step 2!

6. How you divide the problem is key Say you want to count the number of “a”sin a string. How could you solve that problem recursively? Hint: how many “a”s does a string of length 0 have?

7. How you divide the problem is key isPalindrome(String s) abaXaba -> true abba -> true abab -> false