Multidimensional Array | Programming and Data Structures - Computer Science Engineering (CSE) PDF Download

A multi-dimensional array is an array of arrays. 2-dimensional arrays are the most commonly used. They are used to store data in a tabular manner.
Consider following 2D array, which is of the size 3 x 5. For an array of size N x M , the rows and columns are numbered from θ to N - 1 and columns are numbered from θ to M - 1, respectively. Any element of the array can be accessed byarr[i][j]  where θ < i < N and θ < j M. For example, in the following array, the value stored at  is arr[1][3] is 14.

2D array declaration

To declare a 2D array, you must specify the following:
Row-size: Defines the number of rows
Column-size: Defines the number of columns
Type of array: Defines the type of elements to be stored in the array i.e. either a number, character, or other such datatype. A sample form of declaration is as follows:
type arr[row_size][column_size]
A sample C++ array is declared as follows:
int arr[3][5];

1. 2D array initialization: An array can either be initialized during or after declaration.
   The format of initializing an array during declaration is as follows:
   type arr[row_size][column_size] = {{elements}, {elements} ... }
   An example in C++ is given below:
   int arr[3][5] = {{5, 12, 17, 9, 3}, {13, 4, 8, 14, 1}, {9, 6, 3, 7, 21}};
   Initializing an array after declaration can be done by assigning values to each cell of 2D array, as follows.
   type arr[row_size][column_size]
   arr[i][j] = 14
   A C++ example of initializing an array after declaration by assigning values to each cell of a 2D array is as follows:
   int arr[3][5];
   arr[θ][θ] = 5;
   arr[1][3] = 14;
   This is quite naive and not usually used. Instead, the array elements are read from STDIN.
2. Processing 2D arrays: The most basic form of processing is to loop over the array and print all its elements, which can be done as follows:
   type arr[row_size][column_size] = {{elements}, {elements} ... }
   for i from θ to row_size
       for j from θ to column_size
           print arr[i][j]
   A C++ example of looping over the array and printing all its elements is as follows:
   #include <iostream>
   using namespace std;
   int main()
   {
       // Array declaration and initialization
       int arr[3][5] = {{5, 12, 17, 9, 3}, {13, 4, 8, 14, 1}, {9, 6, 3, 7, 21}};
       // Iterate over the array
       for(int i=θ; i<3; i++)
       {
           for(int j=θ; j<5; j++)
           {
               // Print out each element
               cout << arr[i][j];
           }
           // Print new line character after the row is printed in above loop
           cout << endl;
       }
       return θ;
   }
   These methods of declaration, initialization, and processing can be extended to 3D or higher dimensional arrays.