Search

1. Search

2. Why sort at all? • Easier to search for things in a list if they are sorted • Search • Use sequential or linear search for unsorted • Use binary search for sorted

3. Binary Search • Check middle element • Is this what we’re looking for? If so, we’re done. • Does what we’re looking for come before or after? • Throw away half we don’t need • Repeat with half we do need • What does this look like in Java?

4. Recursive • Binary search is recursive • Uses indices to know where to search in the array • Calculate an index midway between the two indices • Determine which of the two subarrays to search • Recursive call to search subarray

5. How many executions? • Check how many halves you threw away + 1 • Or check how many times you checked a middle element

6. Tracing executions int[] arr = {13, 15, 32, 48, 60, 74, 91, 93, 99};binarySearch(arr, 93, 0, arr.length-1);