Multidimensional Arrays in C++

Multidimensional Arrays in C++: An Overview

Multidimensional Arrays in C++

Syntax

dataType arrayName[size1][size2]...[sizeN];

Example

int arr[5][4]; 

Here, an integer type 2D array, arris declared with 5 rows and 4 columns thus a total of 20 integer elements.

In the same manner, as above, a 3D array can be declared.

Example

int arr[2][4][3];

The array arr can store 24 integer elements.

Read More - C++ Interview Interview Questions and Answers

How to initialize a multidimensional array in C++?

• 2D array

int arr[2][3] = {{1, 3, 0}, {-1, 5, 9}};
 
int arr[][3] = {{1, 3, 0}, {-1, 5, 9}};
 
int arr[2][3] = {1, 3, 0, -1, 5, 9};

3D array

int arr[2][3][4] = {
 {{3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23, 2}},
 {{13, 4, 56, 3}, {5, 9, 3, 5}, {3, 1, 4, 9}}
 };

How to access the elements of a multi-dimensional array in C++?

• 2D array

Example

 #include <iostream>
using namespace std;
int main() {
 int arr[2][3] = {{5, 6, 7}, {3, 6, 8}};
 cout << arr[0][2];
 return 0;
}

The coutstatement in the above code in C++ Compiler accesses the value of the element in the first row 0 and third column 2 of the array, arr.

Output

7

• 3D array

Example

#include <iostream>
using namespace std;
int main() {
 int arr[2][3][4] = {
 {{3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23, 2}},
 {{13, 4, 56, 3}, {5, 9, 3, 5}, {3, 1, 4, 9}}
 };
 cout << arr[0][2][3];
 return 0;
}

The cout statement in the above code accesses the value of the element in the first row 0, the third column 2, and the fourth dimension 3of the array, arr.

Output

2

How to change the elements of a multidimensional array in C++?

To change the value of a specific element, refer to the index number in each dimension.

• 2D array

Example

#include <iostream>
using namespace std;
int main() {
 int matrix[2][3] = {{5, 6, 7}, {3, 6, 8}};
 matrix[0][2] = 9;
 cout << matrix[0][2]; // Now outputs 9
 return 0;
}

Output

9

How to traverse a multidimensional array in C++?

• 2D array

• using for loop

  Example

  #include <iostream>
  using namespace std;
  int main() {
   int arr[2][3] = {{5, 6, 7}, {3, 6, 8}};
   int i, j;
  
   for (i = 0; i < 2; i++) {
   for (j = 0; j < 3; j++) {
   cout << arr[i][j] << endl;
   }
   }
   return 0;
  }
  

  Run Code >>

  Output

  5
  6
  7
  3
  6
  8
  

• using for-each loop

  Example

   #include <iostream>
  using namespace std;
  
  int main() {
   int arr[2][3] = {{5, 6, 7}, {3, 6, 8}};
  
   for (const int (&row)[3] : arr) {
   for (int element : row) {
   cout << element << endl;
   }
   }
   return 0;
  }
  

  Run Code >>

  In the above C++ code, we use a range-based for loop to iterate through each row in the 2D array. Again, for each row, we use another range-based for loop to iterate through the elements within that row. const int (&row)[3] species that row is a reference to an array of integers with a size of 3.

  Output

  5
  6
  7
  3
  6
  8
  

Input and Output Multidimensional Array Elements in C++

We can use the cinfunction to take inputs of an array from the user.

• 2D array

Example

#include <iostream>
using namespace std;
int main() {
 int marks[2][3];

 // Prompt user to enter grades
 for (int i = 0; i < 2; i++) {
 cout << "Enter the marks for student " << i + 1 << ":\n";
 for (int j = 0; j < 3; j++) {
 cout << "Subject " << j + 1 << ": ";
 cin >> marks[i][j];
 }
 }

 cout << "The marks entered are:\n";

 // Display entered grades
 for (int i = 0; i < 2; i++) {
 cout << "Student " << i + 1 << ": ";
 for (int j = 0; j < 3; j++) {
 cout << "Subject " << j + 1 << ": " << marks[i][j] << endl;
 }
 }
 return 0;
}

The above program is to print the marks of two students in 3 subjects. The first for loop indicates the student number. The 2nd for loop is used to take the marks of the 3 subjects for the student in the first for loop from the user. In the same way, the two for loops work for printing the output

Output

Enter the marks for student 1:
Subject 1: 95
Subject 2: 88
Subject 3: 92
Enter the marks for student 2:
Subject 1: 78
Subject 2: 85
Subject 3: 90
The marks entered are:
Student 1: Subject 1: 95
Subject 2: 88
Subject 3: 92
Student 2: Subject 1: 78
Subject 2: 85
Subject 3: 90

• 3D array

Example in C++ Online Editor

 #include <iostream>
using namespace std;
int main() {
 int arr[2][3][2];

 cout << "Enter the values as given by the user: \n";

 for (int i = 0; i < 2; ++i) {
 for (int j = 0; j < 3; ++j) {
 for (int k = 0; k < 2; ++k) {
 cin >> arr[i][j][k];
 }
 }
 }

 // Printing values with the proper index.

 cout << "\nDisplaying values:\n";
 for (int i = 0; i < 2; ++i) {
 for (int j = 0; j < 3; ++j) {
 for (int k = 0; k < 2; ++k) {
 cout << "arr[" << i << "][" << j << "][" << k << "] = " << arr[i][j][k] << endl;
 }
 }
 }
 return 0;
}

Output

Enter the values as given by the user:
1
2
3
4
5
6
7
8
9
10
11
12

Displaying values:
arr[0][0][0] = 1
arr[0][0][1] = 2
arr[0][1][0] = 3
arr[0][1][1] = 4
arr[0][2][0] = 5
arr[0][2][1] = 6
arr[1][0][0] = 7
arr[1][0][1] = 8
arr[1][1][0] = 9
arr[1][1][1] = 10
arr[1][2][0] = 11
arr[1][2][1] = 12

Summary