Kotlin: Swap Two Numbers without a Temporary Variable

1. Introduction

In this blog post, we're exploring a classic Kotlin program: swapping two numbers without a temporary variable.

2. Program Overview

This Kotlin program will:

1. Request the user to input two numbers.

2. Capture the numbers provided by the user.

3. Swap the numbers without using a temporary or third variable.

4. Display the swapped values to the user.

3. Code Program

import java.util.Scanner

fun main() {
    // Initialize the Scanner class for user input
    val reader = Scanner(System.in)
    
    // Ask the user to input the first number
    print("Enter the first number: ")
    val a = reader.nextInt()

    // Prompt the user for the second number
    print("Enter the second number: ")
    val b = reader.nextInt()

    // Swap the numbers without using a temporary variable
    a = a + b
    b = a - b
    a = a - b

    // Display the swapped values to the user
    println("After swapping: First number = $a, Second number = $b")
}

Output:

Enter the first number: 5
Enter the second number: 10
After swapping: First number = 10, Second number = 5

4. Step By Step Explanation

1. Scanner Initialization: To capture user input, we make use of the Scanner class from the java.util package. The reader instance represents our scanner object.

2. Capture User Input: Using the print function, the program asks the user for two integer values, storing them in a and b.

3. Number Swapping Technique: Instead of relying on a third variable for swapping, we exploit arithmetic operations:

- The sum of a and b is stored in a.- By subtracting the new a (which is the sum) by the original b, we get the original a value, which we then assign to b.- Finally, by subtracting the new a (still the sum) by the new b (the original a), we derive the original b value, which we assign back to a. The swapping is now complete.

4. Showcase Swapped Values: The program then uses the println function to display the swapped values to the user.