How to Initialize Array With Values Read from a Text File in C++?

How to Read and Write Arrays to/from Files in C++?

In C++, arrays store a fixed-size collection of elements of the same type. We can initialize these elements with any valid value. In this article, we will learn to initialize a C++ array with values read from a text file.

Example:

Input:
Text File = “array.txt”  //  contains 1 2 3 4 5

Output:
// Read the values from the file and initialize the array
 Array: 1 2 3 4 5

Initializing Array with a Text File in C++

To initialize a C++ array with values read from a text file, we can use the std::ifstream for reading from files in a similar way as any other data and then initialize the array using that data.

Approach

Open the file named “array.txt” in read mode.
Read values from the file and initialize the array with these values.
Close the file after reading the values and initializing the array.
Finally, display the elements of the array on the console.

C++ Program to Initialize Array With Values Read from a Text File

The below program demonstrates how we can initialize a C++ array with values read from a text file.

array.txt

1 2 3 4 5

C++

// C++ program to demonstrate how to initialize an array
// with values read from a text file
#include <fstream>
#include <iostream>
using namespace std;

int main()
{
    // Creating an array of size 5
    int arr[5];

    // Opening the file in read mode
    ifstream infile("array.txt");
    if (!infile.is_open()) {
        cerr << "Failed to open file for reading.\n";
        return 1;
    }

    // Reading the values from the file and initializing the
    // array
    for (int i = 0; i < 5; ++i) {
        infile >> arr[i];
    }

    // Closing the file
    infile.close();

    // Displaying the array elements
    cout << "Array elements: ";
    for (int i = 0; i < 5; ++i) {
        cout << arr[i] << " ";
    }
    cout << endl;

    return 0;
}

Output

Array Elements: 1 2 3 4 5

Time Complexity: O(K), here K is the number of array elements.
Auxiliary Space: O(1)

Tags:

#CPP Examples #cpp-array #cpp-file-handling #C++ #C++ Programs #CPP