Meljun Cortes Data Structures Arrays

8/21/2019 Meljun Cortes Data Structures Arrays

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Data Structures

Introduction

LIST

ordered set of a variable number of elements to

which additions and deletions may be made

one of the simplest and most commonly foundtype of data

LINEAR LIST

list which displays the relationship of physicaladjacency

Arrays *Property of STI Page 1 of 21

finite sequence of simple data, items, orrecords

Example

Days of the Week (Monday, Tuesday, Wednesday,Thursday, Friday, Saturday,Sunday)

Values in a Deck ofCards

(2, 3, 4, 5, 6, 7, 8, 9, 10, Jack,Queen, King, Ace)

Floors of a Building Basement, Lobby, Mezzanine,First, Second, Third


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Data Structures

Arrays

ordered collection of data items of the sametype referred to collectively by a single name

Index – each variable or cell in an array

Elements – individual data / items in an array

indicated by the array name followed by itsdimensions appears in a square brackets


Dimensions – an integer from 1 – n called

dimensioned variables

arrayName [0][0]


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Data Structures

Operations in Arrays


Figure 1 Array

Insert

Search Delete


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Data Structures

Operations in Arrays

Insert

Adds item to the indicated place/cell

The process is very fast because it only includesone step

Every data inserted is placed in the first vacantcell

Search

Another process that the algorithm carries out

The red arrow from the figure states where thesearch starts


oves me o ca y ownwar s o searc or eitem

Delete

The algorithm must first locate the item to deleteit

The deleted item causes hole in the array

Hole - one or more cells that have filled cellsabove them

02 14 46 65 17 48 32 09 40 08

0 1 2 3 4 5 6 7 8 9

02 14 46 17 48 32 09 40

0 1 2 3 4 5 6 7 8

08

Item to be deleted


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Data Structures

Basics of Arrays in Java

Arrays are treated as primitive type, they are treatedas objects

use the new operator to declare an array

int[] intArray; // declares a reference to

an arrayintArray = new int[100]; // initialize the array, and

sets intArray to

refer to it


intArray name is a reference to an array and not

the array itself The length field of an array can be used to find the

size in bytes:

the size of an array, when created, can no longer bemodified

int arrayLength =

intArray.length; //find array

length


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Data Structures

Basics of Arrays in Java

Array elements can be accessed through the use ofsquare brackets

temp = intArray[6]; // get contents of seventhelement of array

intArray[7] = 48; // insert 48 into the eightcell


the first element is numbered 0 so that the indices inan array of 10 elements run from 0 to 9

initialize first an array before attempting to access it toavoid syntax error

can initiate an array of primitive type to somethingbesides 0 using:

int[] intArray = {0, 2, 4, 6, 8, 10,

12, 14, 16, 18};

Syntax below gives you a runtime error

autoData[] carArray = new

autoData[4000];


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Data Structures

Exercise



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Data Structures

One-dimensional Array

Array1[j]

Two-dimensional Array

Array1[i][j]

Multi-dimensional Array

Array[i][j][k]…

Dimensionality of an Array



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Data Structures

It is the basic array

A vertical table with number of columns andonly one row

type[] variableName;

An array of ints

int[] intArray;

One-Dimensional Array


Random[] randomArray;

Arrays are fixed-length structure

What is the difference of the two array syntaxbelow?

int[] intArray = new intArray[5];

and

int size = 5;

Random[] randomArray = new

Random[size];


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Data Structures


Index and Length

Indices – used to access each location ofarrays from 0 ranging up to the instantiated

array

An array of length 10, instantiated asint[] intArray = new intArray[10]

Attempting to access an index which is out ofrange, gives you


rray n ex u oun s xcep on

Example

int size = 5;

int[] intArray = new int[size];

for(int index = 0; index < size;

index++)

{ intArray[index] = index; }


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Data Structures


Changing the Size of an Array

Analyze the syntax below and give its output:

int[] intArray = new int[5];

for (int index = 0; index < 3;index ++)

{ intArray[index] = index + 1; }


ow o ma e your array grow an s r n

create a temporary array of the desired size

using for loop, access each item from theoriginal array and save it to thecorresponding index of the temporary array

save the temporary array into the variableof your original array


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Data Structures


Example (continued..)

int[] intArray = new int[5];

for (int index = 0; index < 3;

index ++){ intArray[index] = index + 1; }

int[] tempArray = new int[3];

for (int index = 0; index <


tempArray.length; index++)

{ tempArray[index] =

intArray[index]; }

intArray = tempArray;


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Data Structures

Two-Dimensional Array

It is an array of an array

Also called as tables or matrices

Row – first dimension

Column – second dimension

Arr1[2][3]


Two-Dimensional Array with 3 Rows and 4 Columns


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Data Structures

Two-Dimensional array

declaration and instantiation of 2D array is similar tothat of 1D array

int rows = 3, cols = 4;

int[][] tableArray = new int[rows][cols];

for (int rowIndex = 0; rowIndex < rows;

rowIndex ++)

{for (int colIndex = 0; colIndex <

cols; colIndex ++)

{ tableArray[rowIndex][colIndex] =

rowIndex * colIndex + 1; }


Curly braces is the alternative constructor for 2Darrays

int[][] tableArray = { {1,2,3,4,5},

{6,7,8,9,0} };

For a more look of like a table

int[][] tableArray = { {1,2,3,4,5} }

{ {6,7,8,9,0} };

You can initialize the row dimension without the

columns but not vice versaint[][] tableArray = new int[5][]; //

illegalint[][]

tableArray = new int[][5]; // accepted


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Data Structures


example of a 2D array



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Data Structures


Matrix - is a mathematical object which arisesin many physical problems

consists of m rows and n columns


m x n (read as m by n) is written todesignate a matrix with m rows and n columns


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Data Structures


Magic Square – is an n x n matrix of theintegers 1 to n2


Algorithm to create a magic square by H.Coxeter

Begin with 1 in the middle of the top row Move up and left assigning numbers in

increasing order to empty squares

If you fall off the square imagine the samesquare as tilting the plane and continue

If a square is occupied, move down instead

and continue


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Data Structures


Sample program of Magic Square



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Data Structures


Transpose – another operation that can beperformed on matrices that computes for thetranspose of matrix

the elements in the [i,j ] position aretransferred to the [ j,i ] position

elements in the diagonal will always remainin the same position since i = j


Arr2 matrix

Arr2 transpose matrix


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Data Structures

Linear Search

checks every element of a list one at a time insequence

also called as sequential search

Algorithm for linear search

Create an ordered array

Initialize a target value or the key


If index == key, return true

If index < key, return false

Ordered array


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Data Structures

Binary Search

Usually coded as

mid = (high + low) /2;

Algorithm for binary search

Array elements should be sorted

Find the middle Compare the middle item to the target value or

the key

If not found - read, search parameters, half thesize and start over

Arrays *Property of STI P 21 f 21

If found, return

Meljun Cortes Data Structures Arrays

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