Swap Two Numbers

Given two numbers a and b, the task is to swap them.

Examples:

Input: a = 2, b = 3
Output: 3 2

Input: a = 20, b = 0
Output: 0 20

Input: a = 10, b = 10
Output: 10 10

Using a Third Variable

The idea is to use a third variable, say temp to store the original value of one of the variables during the swap.

Let us understand with an example, a = 10, b = 20

• Store the value of a in temp, temp = 10
• Assign the value of b to a, a = 20
• Assign the value of temp to b, b = 10

// C++ Code to swap two numbers using third variable

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 20;
  
    // Swap a and b using temp variable
    int temp = a;
    a = b;
    b = temp;
  
    cout << a << " " << b << endl;
    return 0;
}

// C Code to swap two numbers using third variable
#include <stdio.h>

int main() {
    int a = 10, b = 20;
    
    // Swap a and b using temp variable
    int temp = a;
    a = b;
    b = temp;
    printf("%d %d\n", a, b);
    return 0;
}

// Java Code to swap two numbers using third variable
public class Main {
    public static void main(String[] args) {
        int a = 10, b = 20;
        
        // Swap a and b using temp variable
        int temp = a;
        a = b;
        b = temp;
        System.out.println(a + " " + b);
    }
}

# Python3 Code to swap two numbers using third variable
a = 10
b = 20

# Swap a and b using temp variable
temp = a
a = b
b = temp
print(a, b)

// C# Code to swap two numbers using third variable
using System;

class Program {
    static void Main() {
        int a = 10, b = 20;
        
        // Swap a and b using temp variable
        int temp = a;
        a = b;
        b = temp;
        Console.WriteLine(a + " " + b);
    }
}

// JavaScript Code to swap two numbers using third variable
let a = 10, b = 20;

// Swap a and b using temp variable
let temp = a;
a = b;
b = temp;
console.log(a + ' '+ b);

20 10

Without a Third Variable – Using Arithmetic Operations

The idea is to store sum in a variable so that we can get both values without third variable.

Let us understand with an example, a = 10, b = 20

• Store the sum of a and b in a, a = a + b = 10 + 20 = 30
• Get the original value of a and store it in b, b = a - b = 30 - 20 = 10
• Get the original value of b and store it in a, a = a - b = 30 - 10 = 20
• Final result: a = 20, b = 10

// C++ Code to swap two numbers using arithmetic operators

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 20;
  
    a = a + b;
    b = a - b;
    a = a - b;
  
    cout << a << " " << b << endl;
    return 0;
}

#include <stdio.h>

int main() {
    int a = 10, b = 20;

    // swap two numbers using arithmetic operators
    a = a + b;
    b = a - b;
    a = a - b;

    printf("%d %d\n", a, b);
    return 0;
}

public class Main {
    public static void main(String[] args) {
        int a = 10, b = 20;

        //swap two numbers using arithmetic operators
        a = a + b;
        b = a - b;
        a = a - b;

        System.out.println(a + " " + b);
    }
}

a = 10
b = 20

#swap two numbers using arithmetic operators
a = a + b
b = a - b
a = a - b

print(a, b)

using System;

class Program {
    static void Main() {
        int a = 10, b = 20;

        //swap two numbers using arithmetic operators
        a = a + b;
        b = a - b;
        a = a - b;

        Console.WriteLine(a + " " + b);
    }
}

let a = 10, b = 20;

//swap two numbers using arithmetic operators
a = a + b;
b = a - b;
a = a - b;

console.log(a + ' '+ b);

20 10

Without a Third Variable – Using Bitwise XOR

The idea is to use the properties of XOR to swap the two variables.

Let us understand with an example, a = 10, b = 20

• Store the XOR of a and b in a, a = a ^ b = 10 ^ 20 = 30
• Get the original value of a and store it in b, b = a ^ b = 30 ^ 20 = 10
• Get the original value of b and store it in a, a = a ^ b = 30 ^ 10 = 20
• Final result: a = 20, b = 10

// C++ Code to swap two numbers using bitwise XOR
#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 20;
    
    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
    
    cout << a << " " << b << endl;
    return 0;
}

// C Code to swap two numbers using bitwise XOR
#include <stdio.h>

int main() {
    int a = 10, b = 20;
    
    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
    
    printf("%d %d\n", a, b);
    return 0;
}

// Java Code to swap two numbers using bitwise XOR
public class Main {
    public static void main(String[] args) {
        int a = 10, b = 20;
        
        a = a ^ b;
        b = a ^ b;
        a = a ^ b;
        
        System.out.println(a + " " + b);
    }
}

# Python3 Code to swap two numbers using bitwise XOR

a = 10
b = 20

a = a ^ b
b = a ^ b
a = a ^ b

print(a, b)

// C# Code to swap two numbers using bitwise XOR
using System;

class Program {
    static void Main() {
        int a = 10, b = 20;
        
        a = a ^ b;
        b = a ^ b;
        a = a ^ b;
        
        Console.WriteLine(a + " " + b);
    }
}

// JavaScript Code to swap two numbers using bitwise XOR

let a = 10, b = 20;

a = a ^ b;
b = a ^ b;
a = a ^ b;

console.log(a, b);

20 10

Using Built-in Swap Methods

We can also swap using built-in functionalities like swap() function in C++, tuple unpacking in Python, destructuring assignment in JavaScript.

// C++ Code to swap two numbers using swap function

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 20;
  
    swap(a, b);
  
    cout  << a << " " << b << endl;
    return 0;
}

#include <stdio.h>
#include <stdlib.h>

void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

int main() {
    int a = 10, b = 20;
    swap(&a, &b);
    printf("%d %d\n", a, b);
    return 0;
}

def swap(a, b):
    return b, a

a = 10
b = 20
a, b = swap(a, b)
print(a, b)

function swap(a, b) {
    return [b, a];
}

let a = 10, b = 20;
[a, b] = swap(a, b);
console.log(a +' ' + b);

20 10