Arrays in C++

One-Dimensional Array

• Arrays store multiple values in a single variable.
• This avoids declaring separate variables for each value.
• Each element is accessed by an index.

What is an Array?

• Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.
• Each element can be accessed by an index.

Declaration of an Array

• Declaring an array means allocating memory to store multiple elements of a given data type.
• Syntax: dataType arrayName[arraySize];

Properties of 1D Array in C++

• Index-Based Access
• Fixed Size
• Linear Structure

Index-Based Access

• Elements are accessed using an index, which is a numeric value indicating the position of the element within the array.
• The index starts from 0 for the first element.
• It goes up to one less than the size of the array.
• For an array with five elements, the indices range from 0 to 4.

Fixed Size

• One-dimensional arrays have a fixed size.
• The size of the array is specified at compile time.
• Once declared with a certain number of elements, the size cannot be changed during runtime.

Linear Structure

• The elements are arranged in a linear or one-dimensional structure.
• There is only one dimension to consider when accessing or arranging the elements.
• Unlike multi-dimensional arrays, which have rows and columns, one-dimensional arrays have a single row or sequence of elements.

How to Use 1D Array in C++

• Usage involves:
  • Declaring the array.
  • Initializing it with values (optional).
  • Accessing and modifying elements.
  • Performing various operations on the array.

Declaring an Array

• To declare an array in C++, specify the data type of the elements followed by the array name and the size of the array in square brackets.
• Example: int arr[5]; declares an array of integers with five elements.

Accessing and Modifying Elements

• Elements are accessed using indices, starting from 0 for the first element.
• You can access and modify elements using square brackets [].
• Example:
  • int value = arr[2]; // Accessing the element at index 2
  • arr[3] = 60; // Modifying the element at index 3 to 60

Example of One-Dimensional Array in C++

#include <iostream>
using namespace std;
int main() {
    int arr[5] = {10, 20, 30, 40, 50};

    // Accessing elements of the array
    cout << "Element at index 2: " << arr[2] << endl;

    // Modifying elements of the array
    arr[3] = 60;
    cout << "Modified element at index 3: " << arr[3] << endl;

    // Calculating the sum of all elements
    int sum = 0;
    for (int i = 0; i < 5; i++) {
        sum += arr[i];
    }
    cout << "Sum of all elements: " << sum << endl;
}

• Output:
  • Element at index 2: 30
  • Modified element at index 3: 60
  • Sum of all elements: 170

Two-Dimensional Arrays

• A 2-dimensional array in C++ is a collection of elements arranged in rows and columns, forming a table or grid-like structure.
• It is essentially an array of arrays where each element is accessed by two indices: one for the row and one for the column.

Two-Dimensional Arrays

• A 2-dimensional array in C++ is a collection of elements arranged in rows and columns, forming a table or grid-like structure.
• It is essentially an array of arrays where each element is accessed by two indices: one for the row and one for the column.

Syntax:

• dataType arrayName[number_of_rows][number_of_columns];

Properties of 2D Array in C++

• Index based access
• Fixed Size
• Processing Elements Row by Row or Column by Column

Index-Based Access

• Elements of the array are accessed using indices.
• The first element is accessed with the index 0, and each subsequent element is accessed with an index that increases by 1.

Fixed Size

• When you declare a 2D or multidimensional array with a fixed size, the number of rows and columns must be known at compile time.
• This means you must specify the size in the declaration

Processing Elements Row by Row or Column by Column

• To access or process all elements of a 2D array, nested loops are commonly used.
• Usually with the outer loop iterating over rows and the inner loop over columns.

Example of Two-Dimensional Array in C++

#include <iostream>
using namespace std;
int main() {
    const int rows = 2;
    const int cols = 3;
    int numbers[rows][cols] = {
        {1, 2, 3},
        {4, 5, 6}
    };

    int sum = 0;

    // Print the array and calculate the sum
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            cout << numbers[i][j] << " ";
            sum += numbers[i][j];
        }
        cout << endl;
    }

    cout << "Sum of all elements: " << sum << endl;
}

• Output:

1 2 3
4 5 6
Sum of all elements: 21