How do you declare a two dimensional array with initialiser in C programming?

Answer 1

#include <iostream>

#include <iomanip>

using std::cout;

using std::endl;

using std::setw;

int main()

{

static const char *Rush[3][2] = {

{ "Geddy Lee", "Vocals, bass and keyboards" },

{ "Alex Lifeson", "Lead/rhythm guitar" },

{ "Neil Peart", "Drums & percussion" }};

cout << "Personnel:" << endl << endl;

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

cout << setw(16) << Rush[nPerson][0] << " : " << Rush[nPerson][1] << endl;

cout << endl;

return( 0 );

}

Answer 2

A simple formula to declare arrays in C++ is as:

1. For 1D or one dimensional array:

data_type name_of_array[size_of_array] ;

For example, if I want to declare a 1D array named marks, of integer type with a size 10, I will write

int marks [10];

2. For 2D or two dimensional arrays:

data_type name_of_array[number_of_rows][number_of_columns] ;

For example, to declare any floating point, 2D array, with 3 rows and 5 columns, I will write

float sample [3][5];

The above methods are fine for static arrays, where the number of elements is known at compile time, but not dynamic arrays, which must be determined at runtime. The following will allocate memory to a one dimensional array of 10 integer elements

int elems = 10; // variable -- can be changed at runtime by whatever means.

int * p = ( int * ) calloc( elems, sizeof( int ));

// use p as you would a static array.

p[1] = 100;

printf( "%d\n", p[1] ); // prints the second element.

// release the allocated memory.

free( p );

2 dimensional dynamic arrays require the use of pointer-to-pointer types. Basically, you create a pointer-to-pointer variable which points to a one-dimensional array of pointers. Each of the pointers in the array points to a one-dimensional array of the actual type. All pointers must be the same type as the type in the array.

// equivalent of a [10][20] array of type float:

int d1 = 10, d2 = 20; // variables -- can be changed at runtime.

float ** pp = ( float * ) calloc( d1, sizeof( float ));

// now instantiate the second dimension:

for( int i = 0; i < d1; ++i )

pp[i] = ( float * ) calloc( d2, sizeof( float ));

// use pp as you would a static array.

pp[1][2] = 199.99;

printf( "%.2f", pp[1][2] );

// Remember to release the 2nd dimension before deleting the main pointer.

for( int i = 0; i < d1; ++i )

free( pp[i] );

free( pp );

Larger multi-dimensional dynamic arrays are created by adding more levels of indirection to the main array pointer. So a 3D dynamic array uses a pointer-to-pointer-to-pointer variable to point to a one-dimensional array of pointer-to-pointer, and each of those pointer-to-pointer elements represents a two dimensional array as shown above. The only thing to remember is that you must release each one-dimensional array in the reverse order it was allocated. So if you have a 3 dimensional array, release the 3rd dimension before releasing the 2nd dimension, then release the main pointer (the 1st dimension).

Answer 3

#include<iostream>

int main()

{

int a[5];

int b[3]={1,2,3};

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

int* d = new int[5];

delete[]d;

}

In the above example, a, b and c are static arrays while d is a dynamic array. a is uninitialised, thus you must initialise each element before using it. b and c are initialised with the given values. Although c has no explicit dimension, 5 elements are specified thus it has an implicit dimension of 5. If you initialise fewer elements than specified by the dimension, the remaining elements are assigned 0. If you initialise more elements than are defined, a compiler errror occurs.

Note that d must be released when no longer required. Note the use of the subscript operator [] to ensure all elements in the array are deleted. If you omit this operator, only the first element is deleted.

In C++, an STL vector can be used instead of a dynamic array. Vectors are objects which makes it much easier to pass arrays by reference into functions, without the need to also pass the size of the array (the size is a private member of the vector object).

Answer 4

Like so:

int x[2][3] = {{00, 01, 02}, {10, 11, 12}};

The above declares a two-dimensional array with 2 rows and 3 columns. Note the whole initialiser is enclosed in braces while each row is also enclosed in braces. This is because each row is a one-dimensional row with 3 elements, thus each must be initialised separately.

Answer 5

the process is same as that for C. char array [10][20];