🔄 Swapping Two Numbers Without Using a Temporary Variable in C++

🔄 Swapping Two Numbers Without Using a Temporary Variable in C++

Swapping two numbers is a fundamental concept in programming, commonly used in algorithms, sorting, and memory management. While the traditional approach uses a temporary variable to hold one value during the exchange, there’s an efficient and elegant method to achieve the same result without using a temporary variable. In this article, we’ll explore how to do this in C++ with a complete example, code explanation, and sample output.

This approach is useful for optimizing memory usage, especially in systems where every byte matters, such as embedded systems or low-level applications. Moreover, understanding such basic logic builds strong problem-solving skills, which are essential for beginners and competitive programmers alike.

💡 What Does It Mean to Swap Without a Temporary Variable?

Swapping without a temporary variable means exchanging the values of two variables without using any additional storage. Instead, we manipulate the original variables using arithmetic operations. There are three common methods to achieve this:

• Addition and Subtraction
• Multiplication and Division
• Bitwise XOR

In this example, we'll focus on the Addition and Subtraction method, which is both easy to understand and widely used.

📄 C++ Code Example

#include <iostream>
using namespace std;

int main() {
    int firstNumber, secondNumber;

    // Input from user
    cout << "Enter the first number: ";
    cin >> firstNumber;

    cout << "Enter the second number: ";
    cin >> secondNumber;

    // Display before swapping
    cout << "\nBefore Swapping:\n";
    cout << "First Number = " << firstNumber << ", Second Number = " << secondNumber << endl;

    // Swapping without using a temporary variable
    firstNumber = firstNumber + secondNumber;
    secondNumber = firstNumber - secondNumber;
    firstNumber = firstNumber - secondNumber;

    // Display after swapping
    cout << "\nAfter Swapping:\n";
    cout << "First Number = " << firstNumber << ", Second Number = " << secondNumber << endl;

    return 0;
}
    

✅ Sample Output

Enter the first number: 5  
Enter the second number: 10  

Before Swapping:  
First Number = 5, Second Number = 10  

After Swapping:  
First Number = 10, Second Number = 5
  

📝 How It Works

Here’s how the logic works step-by-step:

• firstNumber = firstNumber + secondNumber; → firstNumber becomes the sum of both numbers.
• secondNumber = firstNumber - secondNumber; → subtracting the original second number gives the original first number.
• firstNumber = firstNumber - secondNumber; → subtracting the new second number gives the original second number.

No additional memory is used. This is a smart trick for situations where memory is limited or when you want to demonstrate clever logic in interviews or coding challenges.

📘 Definition: Swapping Two Numbers Without Using a Temporary Variable

Swapping two numbers without using a temporary variable is a technique in programming where the values of two variables are exchanged without utilizing any extra storage or third variable. This is accomplished by applying mathematical or logical operations directly on the two variables. Common methods include using arithmetic operations like addition and subtraction, or bitwise operations such as XOR.

This approach is memory-efficient because it eliminates the need for additional memory allocation. It is especially useful in low-level or embedded systems where memory usage must be minimized. Additionally, it demonstrates an understanding of data manipulation and is often used in algorithm design, competitive programming, and technical interviews.