CSE 250CSE 250February 16 - 20, 2009

AnnouncementsAnnouncements2/16 – In-lab Exercise 3 due3/4 - Exam 2

Data Structures 1, 2, 3 are due Friday 3/6. However, those projects will not be considered late as long as they are turned in by the end of the day 3/15.

AnnouncementsAnnouncementsUsing Web-CAT to submit your

assignmentsData Structures 1, 2, and 3 will

need to be submitted using Web-CAT, a new online submission mechanism. Please see ◦http://www.cse.buffalo.edu/faculty/

adrienne/SP2009/cse250/Lectures/SubmissionUsingWeb-CAT.ppt

RecursionRecursionWhat do we know about

recursion?

A recursive function is one that calls itself. Recursive functions have:◦One or more base cases◦A recursive case

Recursive Linear SearchRecursive Linear Searchpublic int linearSearch(Collection<E> items, E toFind,

int index) {

if(items.isEmpty()) return -1;

else if(items[index] == toFind) return index;

else return linearSearch(items, toFind, index+1);

}

Binary SearchBinary Search

int binarySearch(Collection<Elem_Type> items, Elem_Type searchItem)

{

if(items.isEmpty()) return -1; else return binarySearchHelper(items, itemToLookFor, 0,

items.size());}

Binary Search HelperBinary Search Helperint binarySearchHelper(Collection<Elem_Type> items,

Elem_Type searchItem, int start,

int end){if(start > end)return -1;

else { int mid = start+end /2; if(items[mid] == itemToLookFor) return mid; else if (items[mid] < itemToLookFor) return binarySearchHelper(items, itemToLookFor,

mid+1,end); else return binarySearchHelper(items, itemToLookFor,

start, mid-1); }

}

Test CasesTest CasesCome up with test cases for binary search

Trace ThroughTrace ThroughTrace through test cases to

uncover errors (code printed on previous slides fixes errors we found in lecture).

Are there more? More testing could reveal more…

Heaps / Priority QueuesHeaps / Priority Queues