C++ Multi-Dimensional Arrays

🧱 C++ Multi-Dimensional Arrays

A multi-dimensional array in C++ is an array that has more than one dimension.
The most common type is a 2D array, which looks like a table (rows × columns).

🔹 1. 2D Array Declaration

data_type array_name[rows][columns];

Example:

int matrix[2][3];

➡ 2 rows and 3 columns
➡ Total elements = 2 × 3 = 6

🔹 2. 2D Array Initialization

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

🔹 3. Accessing 2D Array Elements

cout << matrix[0][1]; // Output: 2

👉 Indexing starts from 0

🔹 4. Traversing 2D Array Using Nested Loops

for (int i = 0; i < 2; i++) {
for (int j = 0; j < 3; j++) {
cout << matrix[i][j] << " ";
}
cout << endl;
}

Output:

1 2 3
4 5 6

🔹 5. User Input in 2D Array

int mat[2][2];

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

🔹 6. Omit Row Size (Allowed)

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

✔ Column size must be specified

🔹 7. 3D Array Example

int cube[2][2][2] = {
{
{1, 2},
{3, 4}
},
{
{5, 6},
{7, 8}
}
};

Access:

cout << cube[1][0][1]; // Output: 6

🔹 8. Common Operations on 2D Arrays

Sum of All Elements

int sum = 0;

for (int i = 0; i < 2; i++) {
for (int j = 0; j < 3; j++) {
sum += matrix[i][j];
}
}

Matrix Addition

int a[2][2] = {{1,2},{3,4}};
int b[2][2] = {{5,6},{7,8}};
int c[2][2];

for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
c[i][j] = a[i][j] + b[i][j];
}
}

❌ Common Mistakes

int mat[][] = {{1,2},{3,4}}; // ❌ invalid

✔ Correct:

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

🔁 1D vs 2D Array

1D Array2D Array
ListTable
Single loopNested loops
Linear dataGrid data

📌 Summary

  • Multi-dimensional arrays store data in rows & columns

  • Most common: 2D arrays

  • Use nested loops to process data

  • Column size must be specified if row size is omitted

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