2d or 2 dimensional arrays

8/7/2019 2D or 2 Dimensional Arrays

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2D or 2DimensionalArrays

By : Falak Singhal

X1 B



Introduction with 2d Arrays…



What is an array???

“An array is a continued memory allocation that can store manyvalues in memory using one common basic identifier and theindividual values are identified by a number of that allocation”

Individual elements are identified by integer subscripts whichare enclosed in square brackets [] following the array variable.The xi in mathematics is written as x[i] in C++ and most other

programming languages.

E.g. : int abc[10] //declares an array of of int type variables undercommon identifier “abc”.



What is an 2d array???

In common language –” Data that is in rowsand columns is usually stored in 2-dimensionalarrays”

Or“ A 2 dimensional array is an array in whichthere is a collection of one dimensional arrays”

e.g. : int abc[3][2] ; //declares an 2d array of

three 1d

arrays having 2 elements each



Declaration of 2-dimensional -arrays…



Two-dimensional arrays aredeclared by specifying the numberof rows then the number of columns in the following fashion-

<datatype> <identifier> [rows]

[columns]e.g. : int abc[5][4];



The declaration int abc [5][4] will producethe following type of memory allocation :

COLUMN

ROW

0

1

2

3

4

0

1

2

3



Initializing 2-dimensional -arrays…



Unless specified, all initial values of arrays aregarbage. You can specify initial values byenclosing each row in curly braces like this:

char ttt[3][3] = {{'x', 'x', 'o'},{'o', 'o', 'x'},{'x','o', ' '} };

Note that - If some elements are omitted in the

initialization list, they are set to zero.



char ttt[3][3] = {{'x', 'x', 'o'},{'o','o', 'x'},{'x', 'o', ' '}};



int nums[5][4];



Processing 2-dimensional-arrays…



To read or process a 2d array, you need touse nested loops

One loop processes the row and the other,

the columns. If the outer loop is for rowsand the inner loop is for columns, then foreach row index, all columns are processedand then the same process is repeated forthe next row index.

Reading the array



e.g. : int a[2][3]; //array with 2 rows & 3 columnsint i,j;

for(i=0 ; i < 2 ; i++) //loop to control rows

{

for(j=0 ; j < 3 ; j++) //loop to control columns

{ cout <<“enter element “ ;cin >>a[i][j];

}

}



a [0] [0]

a [0] [1]

a [0] [2]

The previous code reads values for all elements. It first reads all columns for row 0

and similarly continues…

Single memory allocation



Application of 2Darrays



void display(int x[3][3])

{

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

{

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

{

cout<<x[i][j]<<'\t';

}cout<<endl;

}

}



void main()

{

clrscr();

int a[3][3],b[3][3],sumab[3][3];

accept(a);

clrscr();

accept(b);

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

{

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

{

sumab[i][j]=a[i][j]+b[i][j];

}

}

clrscr();

cout<<"I MATRIX"<<endl;

display(a);

cout<<"II matrix"<<endl;

display(b);

display(sumab);

getch();

}

2d or 2 dimensional arrays

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