Siti Nurbaya Ismail Senior Lecturer Faculty of Computer

Siti Nurbaya Ismail Senior Lecturer Faculty of Computer & Mathematical Sciences Universiti Teknologi MARA Kedah (e): sitinurbaya@kedah. uitm. edu. my (b): https: //sitinur 151. wordpress. com 1

Array • Differentiate Between Simple Variable And Array • Understand How Computer Executes Algorithm Contains Array • Construct Algorithm Using Array (Maximum, Minimum, Count, Average, Summation) • Apply Sorting And Searching Problem

Introduction • So far, we solve problems using simple variables. • A simple variable can only store one value at one time. • When we assign a new value to the variable, the existing value will be replaced by the new value. Start variable = 10 Display “ initial value = “ , variable = variable + 5 Display “ new value = “ , variable End output

Introduction Start sum 0 Display “ Enter 5 numbers : “ Set counter to 1 While counter ≤ 5 Read num sum + num Add 1 to counter end. While average sum / 5 Display “ the average = “ , average Display newline Display “The numbers entered are : “ Set counter to 1 While counter ≤ 5 Display num , “ “ Add 1 to counter end. While End input 10, 23, 7, 10, 50 tracing table num sum average 0 10 10 23 33 7 40 10 50 50 100 Sometimes, you need to deal with a whole bundle of data, all at once. 50 output variable num will store the last number entered by the user (50). The first four numbers entered are gone. If we want to keep the previous data (the first four entered data), we have to use five variables, instead of only one variable. Simple variable One variable stores one data.

What is Array? • An array lets you manage a whole train of data • Sometimes, you want to refer to a whole bunch of data all at once. For that, you need a new type of variable: the array. • Think of an array as a data train. Each car in the train is called an array element and can store a single piece of data. If you want to store a number in one element and a string in another, you can.

What is Array? • You might think that as you are storing all of that data in an array, you still might need variables for each of the items it stores. • But this is not the case. An array is itself just another variable, and you can give it its own variable name:

What is Array? • Even though an array contains a whole bunch of data items, the array itself is a single variable, which just so happens to contain a collection of data. Once your data is in an array, you can treat the array just like any other variable.

Array • array is one of a complex data • array is a variable that can store more than one data or value at one time because it is allocated with many memory locations as indicated by the size of the array • the data type for each value must be the same • the number of data can be stored in an array is fix Array size is 10

When to use array? • We store the data in the array when: • There are many data with the same data type to be used repeatedly in an algorithm at different places. • There are many data with the same data type that must be retained until the end of the algorithm.

Manipulate An Array • Two types of data; • primitive data • complex data cannot be broken further into smaller data can be broken further. an array is one example of a complex data an array stores a set of data with the same data type that can be broken into a few data from a set of data example: declare a string as coursecode = “love” initialize the string coursecode with values love the string coursecode can be broken into four single characters as l, o, v and e coursecode = l o v e

Manipulate An Array • When an array stores 10 data or value, the array can be broken into 10 different data or element values. first index 0 (at index 8) 1 2 3 4 5 6 7 8 9 9 10 cat element 1 2 3 4 5 6 7 array size is 10 Element Index / Subscript First element 0 Second element 1 Third element 2 Fifth element 3 8

Manipulate An Array index element 0 1 2 3 4 5 … N-1 1 2 3 4 5 6 … N array size is N Note : When the size of array is N, the indexes are 0, 1, 2, …… N-1. We manipulate an array just like we manipulate a variable. We can perform input, process and output to an array.

Declare An Array • declare the array • the name of the array • the size of the array name-of-array [size-of-array] • examples num[5] mark[2] salary[30] name[3]

Declare and Initialize The Array • We can declare and initialize the array at the same time as in the following ways: name-of-array [size-of-array] = {values} or name-of-array [ ] = {values}

Declare and Initialize The Array the size of the array grade is 7 even though the size of the array were not mentioned in the square bracket [ ].

INCORRECT to declare an array with a size less than the number of initialized values. When the size of an array is greater than the number of initialized values, the system will store all the initialized values in the array and the rest of the array will be filled with zero(0) when the type of the array is numeric OR null character (■) when the type of the array is character.

Set Data Into Array • We set data or store value(s) into the array using input statement or assignment statement. • We can assign data into a certain element or give values to an entire array or a portion of the array.

Set Data Into An Element of Array • If we want to set a data or a value into an element, use the following way: name-of-array [which-element] = data // using assignment statement read name-of-array [which-element] // using input statement

Set Data for Entire Array or A Portion of the Array • When we want to set the entire array or a portion of an array, we have to set element by element using a loop control structure.

Set Data for Entire Array or A Portion of the Array • set element by element using a loop control structure.

Display An Array Display an element of an array as follows: i. Display name-of-array [ which element ] Example: display num[4]// the content of the fifth element will be displayed OR // the content of element at index 4 will be displayed ii. Display the entire of array elements one by one using a loop control structure.

Basic Algorithms Using Array Calculate the total of data in the array

Basic Algorithms Using Array Calculate the average of data in the array

Basic Algorithms Using Array Find the maximum value in the array

Basic Algorithms Using Array Find the minimum value in the array

Basic Algorithms Using Array Counting ( to count how many certain data exists in the array )

0 50 Basic Algorithms Using Array 80 50 88 Determine how many students in the class KCS 1101 C pass in the second test. Assume that there are 30 students in the class. Passing mark is 50. List all the pass marks. 30 88 45

Basic Algorithms Using Array Searching ( to find whether a certain data is in the array or not ) Example to find whether 88 is in the array or not. • Solution 1: Use count algorithm • Solution 1: Use break

Start array. Size = 10 Num[array. Size] Solution 1 //segment to input data Set ind with 0 While ind < array. Size read Num[ind] increase ind by 1 end. While //count how many 88 in the array count 88 = 0 Set index with 0 While index < array. Size if ( Num[index] == 88 ) count 88 = count 88 + 1 End. IF increase index with 1 end. While if ( count 88 == 0 ) Display “ 88 is NOT in the array “ Else Display “ 88 is in the array “ End. IF End When we compare these two solutions, Solution 1 and Solution 2, in terms of the number of iteration, Solution 1 does iteration for array. Size times. Meanwhile Solution 2 stops the iteration when the data was found. It means that the maximum number of iteration is array. Size times. BUT when the data was found, the number of iteration is lesser. Start array. Size = 10 Num[array. Size] Solution 2 //segment to input data Set ind with 0 While ind < array. Size read Num[ind] increase ind by 1 end. While //determine whether 88 is in the array or not found = 0 set ind with 0 while ( found is 0 AND ind < array. Size ) if ( Num[ind] == 88 ) found = 1 break End. IF increase ind by 1 end. While if ( found == 1 ) Display “ 88 in the array “ Else Display data “ 88 not in the array “ End. IF End Note: statement break is to jump out from the loop when the condition ( num[ind] == 88 ) is true

Sort Data • Sorting is a process that takes in an unordered collection and makes it an ordered one, either in ascending order or descending order. Many methods can be implemented to sort data such as bubble sort, heap sort, binary sort, etc

Sort Data: Bubble Sort: Ascending & Descending • Ascending order Start array. Size = 10 Num [array. Size ] //segment to input data : : //sort data in ascending order Set outer with 0 While outer < array. Size Set inner with outer + 1 While inner < array. Size - 1 if ( Num[ inner ] > Num [outer ] ) • Descending order if ( Num[ inner ] < Num [outer ] ) temporary = Num[ inner ] = Num[ outer ] = temporary End. IF increase inner by 1 end. While add 1 to outer end. While //display sorted data Set index with 0 While index < array. Size Display Num[index] Increase index by 1 end. While End

Execution of Algorithm Uses Array • Refer Tutorial

EXERCISE 1

EXERCISE 2

EXERCISE 3

The End