CHP 05 Arrays

8/8/2019 CHP 05 Arrays

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C#


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ARRAYS

In C#, arrays is a data structure.

An array is a collection of data having same datatype, storage class and name; and resides inconsecutive memory locations

The individual array elements are distinguishedby an index value, which starts with zero.

This means, the highest index number of anarray is always the no of elements minus one.

Array type can be of any type.


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ARRAYS In C#

In C#, Arrays are a collection of objects or datatypes, which are stored in memory cells.

All the elements of an array must be of the sametype.

In C#, array element type is any one of theprimitive data type or any reference type.

In C# arrays are treated as objects havingSystem.Array as their base class

C# supports two types of arrays. Single Dimensional Arrays

Multi dimensional Arrays


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The general form for creating an array in C# is:Syntax: element-type[ ] name;

name = new element-type[n];

Here, the first statement declares an array.

The second statement allocates memory spacefor n elements.

C# allows you to have a declaration and allocation

in a single statement like below:Syntax:

element-type[ ] name = new element-type[n];

Single Dimension Array


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Examples:

float[ ] amt = new float[6];

char[ ] cx = new char[9];

string[ ] s;

s = new string[8];

box [] bx = new box[7];

Once memory is allocated, all the elements ofarrays are initialized to their default values.

Single dimension array can be initialized whiledeclaring or separately after declaring.

We can find out the number of elements in anarray using Array.Length property


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Initialization

Syntax:

type [] x = new type[n];

x [0]= e1;

x [1]= e2;

.

.

x [n-1]= en;

EX:

int [] x = new int[2];

x[0]= 10;

x[1]=11;



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Initialization

Syntax:

type[] x = {e1, e2, e3, .eN};

Here the size of the array is determined by the number ofelements listed in { }.

The above initialization can be done using new operator

type[] x = new type[ ]{e1, e2, e3, .eN};

Alternative syntax can also be used:

type[] x = new type[ N]{e1, e2, e3, .eN-1};



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Iterating through array

int [ ] x = {1,2,3,4,5,6};

for (int i = 0; i


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MULTI DIMENSIONAL ARRAY

Multi Dimensional arrays can be either: Rectangle Array

Jagged Array

Multidimensional arrays are nothing but, array of

arrays.

In rectangular array, all the arrays at one levelmust have the same dimensions

In Jagged array, all the arrays at one level neednot have same dimensions


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Two dimensional array:

Declaration:

type [,] xy = new type [m,n];

type [,] xy;

xy = new type [m,n];Initialization

Individual elements

type [,]xy = {{e1,e2}, {e3,e4}, . {eN-1,eN}};

type [,]xy = new int[n, m]{{e1,e2}, {e3,e4}, . {eN-1,eN}};

Rectangle Array


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Rectangle Array

Rectangle Array

Initializing example:

int [,] xy = new int[2,2]; // length 4, rank 2

xy[0,0] = 34; xy[0,1] = 24;

xy[1,0] = 44; xy[1,1] = 45;

int [,] xy = {{24,34},{44,45}};

int [,] xy = new int [2,2] {{24,34},{44,45}};

Length property of returns the total number ofelements in the array.


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Three dimensional array:

int [, ,] xyz = new int [n1, n2, n3];

Four dimensional array:

int [, , ,] xyz = new int [n1, n2, n3, n4];

The number of commas in the declaration will beone less than the dimensions (rank) of the array.

We can find out the rank of an array usingArray.Rank property

We can use GetLength method to get the size ofeach dimension.

Arrayname.GetLength(dimension-postion); postion startsfrom 0

Rectangle Array


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int [ ,] x = new int [2,3]{{1,2},{3,4},{5,6}};

for (int i = 0; i


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Jagged arrays are used when we needmultidimensional array, but where the size ofinternal arrays is not same.

Declaration:

type [] [] x; Declares a single dimensional arrayof single dimensional arrays.

type [] [ , ] x; Declares a single dimensional arrayof two dimensional arrays.

type [] [ , ] [] x; Declares a single dimensional arrayof two dimensional arrays ofsingle dimensional arrays.

Jagged Array


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Example:int [] [] x = new int [4] []; // length is 4, rank is 1

x [0] = new int [3]{1,2,3};

x [1] = new int [2]{1,2};

x [2] = new int [5]{1,2,3,4,5};x [3] = new int [7]{1,2,3,4,5,6,7};

Jagged arrays can not be initialized whiledeclaring them like other arrays.

Rank property of a jagged array return the rank ofthe first array.

int [,] [] [,,] x ; //Rank of this array is 2

Jagged Array


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int [] [] x = new int [3] [];

x [0] = new int [3]{1,2,3};

x [1] = new int [2]{1,2};

x [2] = new int [5]{1,2,3,4,5};

foreach (int[] i in x)

foreach(int j in i)Console.WriteLine(j);

Jagged Array

CHP 05 Arrays

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