Data Structures & Algorithms Lecture 3 & 4: Searching and Sorting Algorithm Halabja University Collage of Science /Computer Science Department Karwan Mahdi
[email protected] 2020-2021 Objectives Introduction to Search Algorithms which is consist of Linear Search and Binary Search Understand the significance of sorting Distinguish between internal and external sorting Understand the logic behind the simple sorting methods of bubble sort, selection sort, and insertion sort. Introduction to Search Algorithms Search: locate an item in a list of information. Two common algorithms (methods): • Linear search • Binary search Linear search: also called sequential search. Examines all values in an array until it finds a match or reaches the end. • Number of visits for a linear search of an array of n elements: • The average search visits n/2 elements • The maximum visits is n • A linear search locates a value in an array in O(n) steps Example for linear search Example: linear search Algorithm of Linear Search Order in linear search Advantages and Disadvantages • Benefits: • Easy algorithm to understand • Array can be in any order • Disadvantages: • Inefficient (slow): for array of N elements, examines N/2 elements on average for value in array, • N elements for value not in array “Java code for linear search REQUIRE” Binary Search Binary search is a smart algorithm that is much more efficient than the linear search ,the elements in the array must be sorted in order 1. Divides the array into three sections: • middle element • elements on one side of the middle element • elements on the other side of the middle element 2.