Write a Program to Swap two numbers without using any third variable

Approach 2: Swap numbers by using Bitwise XOR operator

We can swap two numbers without using third variable using Bitwise XOR Operator. 

Let’s first see an example of an XOR operation on two binary numbers.

a = 3 => 0011 in binary.

b = 5 => 0101 in binary.

XOR of a and b is 0110.

Implementation in C++

• C++

C++

#include <iostream>
using namespace std;
 
void swap(int &a, int &b)
{
    if (a != b)
    {
        a = a ^ b;
        b = a ^ b;
        a = a ^ b;
    }
 
}
 
int main()
{
    int a = 3, b = 5;
    swap(a, b);
 
    cout << "After Swapping two numbers: a =" << a << ", b=" << b;
 
    return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

After Swapping two numbers: a = 5, b= 3

Complexity Analysis

Time Complexity: O(1); since we are using bitwise XOR operation, these operations take constant time. So, the time complexity is constant.

Space Complexity: O(1); since we are not using any extra space to store the numbers, the space complexity is also constant.

Approach 3: Swap numbers by using single line expressions

In our third approach, we will use Single Line Expressions to swap two numbers without using third variable.

We can also use any of the given Single Line Expressions to swap two numbers in a single line:

→ x = x ^ y ^ (y = x);

→ x = x + y – (y = x);

→ x = (x × y) / (y = x);

Implementation in C++

• C++

C++

#include <iostream>
using namespace std;
 
void swap(int &a, int &b)
{
    // a = a ^ b ^ (b = a);
    // a = a + b - (b = a);
    a = (a * b) / (b = a);
}
 
int main()
{
    int a = 3, b = 23;
    swap(a, b);
 
    cout << "After Swapping two numbers: a =" << a << ", b=" << b;
 
    return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

After Swapping two numbers: a = 23, b= 3

Complexity Analysis

Time Complexity: O(1); these single-line operations take constant time. So, the time complexity is constant.

Space Complexity: O(1); since we are not using any extra space to store the numbers, the space complexity is also constant.

Check out this problem - XOR Queries On Tree
Also read -  Decimal to Binary c++

Frequently Asked Questions

What are the 3 methods to swap two numbers?

Three common methods to swap two numbers are using a third variable, using arithmetic operations, and using bitwise XOR.

What is swapping?

Swapping is the process of interchanging the values of two variables, effectively exchanging their contents.

What is the process of swapping?

The process of swapping involves temporarily storing the value of one variable, assigning the value of the second variable to the first, and then assigning the stored value to the second variable.

What is required for swapping?

Swapping requires two variables that you want to exchange their values and a temporary storage location (variable) to hold one of the values during the exchange process.

What do you mean by XOR Operations?

XOR operation is a basic boolean logic operation. Two input bits are compared via XOR, which produces one output bit. The Logic of the XOR operation is very simple. When the bits match, the outcome is 0. When the bits vary, the outcome is 1.

What is the Swap() function?

The Swap() is a built-in function in C++ STL. The function accepts two required parameters, x and y, which must be swapped. The function simply swaps the values of the two variables and doesn't return anything. We can use any data type for the parameters. The syntax is swap(x,y). 

Conclusion

We ran through three approaches to swap two numbers without using third variable. We started using the arithmetic operators to swap two numbers. Further, we discussed programs using bitwise XOR operators and Single-line Expressions to swap two numbers without using third variable.

We hope this blog helped you to explain how to write a program to swap two numbers without using third variable. We recommend you visit our articles related to swapping two numbers, such as

• Swapping of two numbers.
• Program to swap two numbers.
• C program to swap two numbers.

You can refer to our Guided Path to upskill yourself in Data Structures and Algorithms, Competitive Programming, System Design, and many more!

Head over to our practice platform Code360 to practice top problems, attempt mock tests, read interview experiences and interview bundles, follow guided paths for placement preparations, and much more!!