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Russian Peasant (Multiply two numbers using bitwise operators)
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Swap Two Numbers Without Using Third Variable

Last Updated : 26 Dec, 2024
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Given two variables a and y, swap two variables without using a third variable. 

Examples:

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

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

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

Table of Content

  • Using Arithmetic Operators
  • Using Bitwise XOR
  • Built-in Swap

Using Arithmetic Operators

  • Store the sum of a and b in a (a = a + b).
  • Get the original value of a, that is (sum – original value of b)and store it in b (b = a – b).
  • Get the original value of b, that is (sum – original value of a)and store it in a (a = a – b).
C++ 
// C++ Code to swap two numbers using arithmetic operators  #include <iostream> using namespace std;  int main() {     int a = 2, b = 3;     cout << "a = " << a << " b = " << b << endl;           a = a + b;     b = a - b;     a = a - b;        cout << "a = " << a << " b = " << b << endl;     return 0; }
C 
// C Code to swap two numbers using arithmetic operators  #include <stdio.h> int main() {     int a = 2, b = 3;     printf("a = %d b = %d\n", a, b);           a = a + b;     b = a - b;     a = a - b;        printf("a = %d b = %d\n", a, b);     return 0; }
Java 
// Java Code to swap two numbers using arithmetic operators  class GfG {     public static void main(String[] args) {         int a = 2, b = 3;         System.out.println("a = " + a + " b = " + b);                   a = a + b;         b = a - b;         a = a - b;                System.out.println("a = " + a + " b = " + b);     } }
Python 
# Python Code to swap two numbers using arithmetic operators  if __name__ == "__main__": 	a = 2 	b = 3 	print("a =", a, " b =", b)      	a = a + b 	b = a - b 	a = a - b      	print("a =", a, " b =", b)
C# 
// C# Code to swap two numbers using arithmetic operators  using System;  class GfG {     static void Main() {         int a = 2, b = 3;         Console.WriteLine("a = " + a + " b = " + b);                   // Swap a and b using arithmetic operators         a = a + b;         b = a - b;         a = a - b;                Console.WriteLine("a = " + a + " b = " + b);     } }
JavaScript 
// JavaScript Code to swap two numbers using arithmetic operators  let a = 2, b = 3; console.log("a = " + a + " b = " + b);     a = a + b; b = a - b; a = a - b;  console.log("a = " + a + " b = " + b);

Output
a = 2 b = 3 a = 3 b = 2

Time Complexity: O(1)
Auxiliary Space: O(1)

Using Bitwise XOR

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

  • a = a ^ b: Store the Bitwise XOR of a and b in a. Now, a holds the result of (a ^ b).
  • b = a ^ b: Bitwise XOR the new value of a with b to get the original value of a. This gives us, b = (a ^ b) ^ b = a.
  • a = a ^ b: Bitwise XOR the new value of a with the new value of b (which is the original a) to get the original value of b. This gives us, a = (a ^ b) ^ a = b.

Finally, a and b hold the swapped values.

C++ 
// C++ Code to swap two numbers using bitwise XOR  #include <iostream> using namespace std;  int main() {     int a = 2, b = 3;     cout << "a = " << a << " b = " << b << endl;           a = a ^ b;     b = a ^ b;     a = a ^ b;        cout << "a = " << a << " b = " << b << endl;     return 0; }
C 
// C Code to swap two numbers using bitwise XOR  #include <stdio.h> int main() {     int a = 2, b = 3;     printf("a = %d b = %d\n", a, b);           a = a ^ b;     b = a ^ b;     a = a ^ b;        printf("a = %d b = %d\n", a, b);     return 0; }
Java 
// Java Code to swap two numbers using bitwise XOR  class GfG {     public static void main(String[] args) {         int a = 2, b = 3;         System.out.println("a = " + a + " b = " + b);                   a = a ^ b;         b = a ^ b;         a = a ^ b;                System.out.println("a = " + a + " b = " + b);     } }
Python 
# Python Code to swap two numbers using bitwise XOR  if __name__ == "__main__": 	a = 2 	b = 3 	print("a =", a, " b =", b)      	a = a ^ b 	b = a ^ b 	a = a ^ b      	print("a =", a, " b =", b)
C# 
// C# Code to swap two numbers using bitwise XOR  using System;  class GfG {     static void Main() {         int a = 2, b = 3;         Console.WriteLine("a = " + a + " b = " + b);                   // Swap a and b using arithmetic operators         a = a ^ b;         b = a ^ b;         a = a ^ b;                Console.WriteLine("a = " + a + " b = " + b);     } }
JavaScript 
// JavaScript Code to swap two numbers using bitwise XOR  let a = 2, b = 3; console.log("a = " + a + " b = " + b);     a = a ^ b; b = a ^ b; a = a ^ b;  console.log("a = " + a + " b = " + b);

Output
a = 2 b = 3 a = 3 b = 2

Time Complexity: O(1)
Auxiliary Space: O(1)

Built-in Swap

We can also swap using built-in functionalities like swap method in C++, tuple unpacking in Python, destructuring assignment in JavaScript. To know more about the implementation, please refer Swap Two Numbers.




Next Article
Russian Peasant (Multiply two numbers using bitwise operators)
author
kartik
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Article Tags :
  • Bit Magic
  • DSA
  • Mathematical
  • Bitwise-XOR
  • Swap-Program
Practice Tags :
  • Bit Magic
  • Mathematical

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