This preview shows pages 1–10. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Searching and Sorting CSE 114: Computer Science I 1 Searching and Sorting • Searching and sorting are among the most common operations performed • Ex. databases • It’s much easier to search data that has been sorted • Ex. searching a telephone directory • Compare to a linear search 2 Linear Search • Examine each element in turn to see if it’s the one you’re looking for • On average, you have to examine half of all elements • Works even if the list is unsorted • Takes time proportional to O(n) (linear) 3 Linear Search Code public boolean search (int list, int value) { for (int i = 0; i < list.length; i++) { if (list[i] == value) return true; } return false; } 4 Binary Search • Method: choose an element at random (usually the middle) and decide whether to search the left or right half • Ex. Searching a dictionary for a word • At each decision point, the space to be searched is cut in half • Requires sorted data to work properly • Very efFcient: only needs log(n) comparisons 5 Pseudocode If (range contains only one element): Look for desired value Else: 1. Get midpoint of range 2. Determine which half of range contains the value 3. Search that half of the range using binary search 6 Binary Search Example • Ex. Find 29 • Start: [10, 13, 14, 29, 37] • Examine 14: [10, 13] [14] [29, 37] • Find 29: [10, 13, 14] [29] [37] 7 Binary Search Code // Iterative binary search algorithm // Search list from indices Frstlast public int binSearch (int list, int value) { int Frst = 0; last = list.length  1; int position = 1; boolean found = false; 8 while (!found && Frst <= last) { int middle = (Frst + last) / 2; if (list[middle] == value) { found = true; position = middle; } 9 else if (array[middle] > value) // search left...
View
Full
Document
This note was uploaded on 04/07/2008 for the course CSE 114 taught by Professor Tashbook during the Spring '08 term at SUNY Stony Brook.
 Spring '08
 TASHBOOK
 Computer Science, Databases, Sort

Click to edit the document details