Lab Manual. CPCS204 Data Structures 1. Lab /1436H

Transcription

1 KING ABDULAZIZ UNIVERSITY Faculty of Computing & Information Technology Department of Computer Science Lab Manual CPCS204 Data Structures /1436H Lab - 3 Learning Procedure 1) Stage J (Journey inside-out the concept) 2) Stage a 1 (apply the learned) 3) Stage v (verify the accuracy) 4) Stage a 2 (assess your work)

2 Laboratory 3: Statement Purpose: This lab will give you the description and implementation some basic Searching and Sorting Algorithms. Activity Outcomes: This lab teaches you the following topics: Learn some well-known sorting algorithms with their implementations. Use of Java.util.Arrays class and its under-class methods sort and binarysearch. Programming practice on sort methods for sorting array elements. Instructor Note: As pre-lab activity, review Ch2 & Ch14, from the book Data Structures with Java by John R. Hubbard and also the relevant instructor s slides. Names I.D CPCS204 The Lab Note Lab-3 1

3 1) tage J (Journey) Sorting Algorithms: A. Selection Sort Methodology (Ascending): Algorithm (implemented in JAVA): public static void selectionsort (int[] list) { int index, smallestindex, minindex, temp; { for (index = 0; index < list.length - 1; index++) smallestindex = index; for (minindex= index+ 1; minindex< list.length; minindex++) {if (list[minindex] < list[smallestindex]) smallestindex = minindex; temp = list[smallestindex]; list[smallestindex] = list[index]; list[index] = temp; CPCS204 The Lab Note Lab-3 2

4 B. Bubble Sort Methodology: Algorithm (implemented as JAVA code): public static void bubblesort(int[] list) { int temp, counter, index; for (counter = 0; counter < list.length; counter++) { for (index=0; index<list.length counter; index++) { if(list[index] > list[index+1]) { temp = list[index]; list[index] = list[index+1]; list[index+1] = temp; //end bubblesort CPCS204 The Lab Note Lab-3 3

5 Searching Algorithms: A. Linear Search linear search does O(n) comparisons on average. B. Binary Search Binary search does O(log n) comparisons at most which is much better than linear search. CPCS204 The Lab Note Lab-3 4

6 2) Stage a 1 (apply) Example 1: Built-in JAVA binarysearch() A static method of the class Arrays for searching the array element in the given arrays. Uses the binary search algorithm. Returns the index of the found element, but if element is not found then returns (-1) Applicable to arrays of any data type object. Array used in binarysearch() must be sorted. The binarsearch() method with Unsorted arrays may give wrong result. Array having duplicate elements when searched by binarysearch() method may return any of the duplicate element. Syntax: public static int binarysearch(object[] array, Object key) Task 1: Write a statement to import the library of Arrays to the below program Task 2: Write and use a linearsearch() method to find index p of key in ar1 Task 3: Write a statement using binarysearch() to find index p of key in ar1 Task 4: Write a statement using to sort ar1 then use again binarysearch() to find index p of key in ar1 //Answer task 1 here import java.util.arrays; public class binary_search { //Answer task 2 here public static int linearsearch(int[] number,int key) { int searchindex=-1,i; for (i = 0; i < number.length; i++) { if (number[i] == key) /* Searching element is present */ {searchindex=i; break; if (i == number.length) /* Searching element is absent */ searchindex=-1; return searchindex; CPCS204 The Lab Note Lab-3 5

7 public static void main(string[] args) { int ar1[]={2,44,5,66,78,90,23,66; int p, key=78; //Answer task 2 here p= linearsearch(ar1,key); //Answer task 3 here p= Arrays.binarySearch(ar1,key) ; System.out.println("element found at index "+p); //Answer task 4 here Arrays.sort(ar1); p= Arrays.binarySearch(ar1,key) ; System.out.println("element found at index "+p); Example 2: Built-in JAVA sort() The sort operation uses a slightly optimized Dual-Pivot Quick sort algorithm that is stable and faster than traditional One-Pivot counterpart. Runs in O(n log n)time. Applicable to List objects consisting numbers or alphabetical content. Syntax: public static void sort(object[] a) or public static void sort(object[] a, int fromindex, int toindex) Task 1: Use the built-in JAVA sorting method for an array's elements. Besides, printing array elements at once without loop (i.e. for or while etc.) (Retype and try this code) Task 2: Clone (copy) array old to new array Arr then use sort(object[] a, int fromindex, int toindex) to sort the right-half of array Arr. Print Arr after sort. //Answer task 1 here import java.util.arrays; import java.util.random; /**program showing some Arrays library uses*/ CPCS204 The Lab Note Lab-3 6

8 public class ArrayTest { /** args the command line arguments */ public static void main(string[] args) { int num[]=new int[10]; Random rand=new Random(); //a pseudo-random number generator rand.setseed(system.currenttimemillis()); //use current time as a seed //fill the num array with pseudo-random numbers from 0 to 99, inclusive for(int i=0;i<num.length;i++) num[i]=rand.nextint(100); int[] old= (int[]) num.clone(); //cloning the num array System.out.println("arrays equal before sort: "+Arrays.equals(old, num)); Arrays.sort(num); //sorting the num array (old is unchanged) System.out.println("arrays equal after sort: "+Arrays.equals(old, num)); System.out.println("Old ="+Arrays.toString(old)); System.out.println("num ="+Arrays.toString(num)); //Task2 //Answer task 2 here int[] Arr= (int[]) old.clone(); //cloning the old array Arrays.sort(Arr,5,10); System.out.println("Arr ="+Arrays.toString(Arr)); CPCS204 The Lab Note Lab-3 7

9 Potential Output: old = [41,38,48,12,28,46,33,19,10,58] // the random generated array num = [10,12,19,28,33,38,41,46,48,58] // sorted array Arr = [41,38,48,12,28,10,19,33,46,58] // sorted right-half of array CPCS204 The Lab Note Lab-3 8

10 3) Stage v (verify) Programming Exercises Ex-1: 1. Write a program that reads 10 integer numbers and sort them with 2 different sorting algorithms. 2. Create 2 public classes. One called TestSorting and the other called Sorting. 3. Sorting class includes above 2 sorting methods (i.e. Selection, and Bubble) and 1 more method for printing the sorted array. 4. TestSorting class includes the main method, and uses java.util.scanner to enter 10 integers. 5. Create and object of class Sorting Sort=new Sorting(). 6. Then it calls the 2 methods in class Sorting then print the original array and the 2 sorted arrays. So, the output would be such that: Please enter a num[0]: 5 Please enter a num[1]: 6 Please enter a num[2]: 9 Please enter a num[3]: 7 Please enter a num[4]: 2 Please enter a num[5]: 4 Please enter a num[6]: 3 Please enter a num[7]: 8 Please enter a num[8]: 10 Please enter a num[9]: 13 The ORIGINAL array is: Sorted array by SELECTION sort is: Sorted array by BUBBLE sort is: Ex-2 (home activity): (Sales Commissions) Use a one-dimensional array to solve the following problem: A company pays its salespeople on a commission basis. The salespeople receive $200 per week plus 9% of their gross sales for that week. For example, a salesperson who grosses $5000 in sales in a week receives $200 plus 9% of $5000, or a total of $650. Write an application (using an array of counters) that determines how many of the CPCS204 The Lab Note Lab-3 9

11 salespeople earned salaries in each of the following ranges (assume that each salesperson's salary is truncated to an integer amount): $ $ $ $ $ $ $ $ $1000 and over Summarize the results in tabular format. 4) Stage a 2 (assess) Lab Work: In each laboratory you are assessed on your work within lab session based on your participation, discussions and achievement of lab activities. Thus, each lab has a portion of the (LAB WORK MARK). Therefore, a checklist of each lab is used to evaluate your work. This checklist accounts the following criteria: Following the lab manual step by step Answering given questions concisely and precisely Practicing and implementing given examples correctly Writing code of required programming tasks Being focused, positive, interactive and serious during lab session Asking good questions or answering instructor questions if any Note: performing given home activities or extra programming is highly recommended to improve your understanding, capability and programming skills. CPCS204 The Lab Note Lab-3 10