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Understanding Recursion and Linked Lists: A Comprehensive Recitation

This recitation, led by Ben Stoddard and Tabitha Peck, covers the essential concepts of recursion and linked lists. Participants will learn why recursion is advantageous and explore different methods, both recursive and non-recursive, especially when managing linked lists. Key topics include base cases, helper methods, and the practical application of these concepts. The session aims to enhance problem-solving skills with a focus on private variables, getter/setter methods, and helper functions. Complete the assigned tasks to deepen your understanding and prepare for future assessments.

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Understanding Recursion and Linked Lists: A Comprehensive Recitation

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  1. Recitation 8Recursion and Linked Lists Ben Stoddard Tabitha Peck March 7, 2014

  2. Covered in this recitation • Recursion • Linked Lists • Recursion + Linked Lists

  3. Why recursion? • Many of these methods would work better with loops. • Recursion will be very useful to you later (trees, midterms, finals) though, so it’s better to practice now. • These problems are another chance to think about how recursion works. What are your base cases? How do you simplify the problem?

  4. Unique to this recitation • Private Variables • Using Getter/Setter methods • Private Helper Methods • User calls the public method for the answer, and the public method uses the private helper methods • In this recitation, the helper methods will be recursive (see next slide)

  5. Add to tail Non-Recursive Recursive public void addToTail(int value){    if(head == null) {        head = new IntListNode(value);    } else { addToTail(value, head);    }        size++; } private void addToTail(int value, IntListNode n) {    if(n.getNext() == null) { n.setNext(new IntListNode(value));    } else { addToTail(value, n.getNext());    } } public void addToTailNoRecursion(int   value) {    if(head == null) {        head = new IntListNode(value);    } else { IntListNode current = head;        while(current.getNext() != null) {            current = current.getNext();        } current.setNext(new IntListNode(value));    }    size++; } ← Base Case: Empty List ← Base Case: Empty List ← Call recursive helper ← Loop to advance ↑ Add new ← Base Case: No next ↑ Recursive case: call with next node (loop advance)

  6. What you will do • Complete the recursive private helper functions • Contains: Check for a value. • countOccurences: Counts a value. • sum: Sums the list. • sumEven: Sums only the even values in the list. • reverseList: Reurns the same list, but in reverse order. • mergeLists: Merges this list with another and returns the resulting list. • *Assumes both lists are sorted. Result should be sorted as well.

  7. Go for it! • You shouldn’t have to change any given code. • You should be able to pass unit tests if you are done. • These slides are online for your reference. • Please do as much as you can and ask UTAs for help. Submit before March 21 (your next recitation).

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