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Python Program to swap two numbers without using third variable

  • Difficulty Level : Hard
  • Last Updated : 16 Nov, 2020

Given two variables n1 and n2. The task is to swap the values of both the variables without using third variable.
Examples: 
 

X : 10
Y : 20
 
After swapping X and Y, we get :

X : 20
Y : 10


 

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 A :  'Hello'
 B :  'World'
  
After swapping A and B, we get : 

 A :  'World'
 B :  'Hello'


Method 1 :- Using simple built-in method 
 



left , right = right , left 


This method works for any data type values like string, int, float and is easy to use. 
 

Python




# Python code to swap two numbers
# without using another variable
 
 
x = 5
y = 7
 
print ("Before swapping: ")
print("Value of x : ", x, " and y : ", y)
 
# code to swap 'x' and 'y'
x, y = y, x
 
print ("After swapping: ")
print("Value of x : ", x, " and y : ", y)

Output: 
 

Before swapping: 
Value of x :  5  and y :  7
After swapping: 
Value of x :  7  and y :  5    


Method 2 :- Using Bitwise XOR operator 
 

x ^= y
y ^= x
x ^= y


This method only works for integers and works faster because this method uses bit operation (for same values, output = 0 and for different values, output = 1) .
 

Python




# Python code to swap two numbers
# using Bitwise XOR method
 
 
x = 5  # x = 0101
y = 10 # y = 1010
 
print ("Before swapping: ")
print("Value of x : ", x, " and y : ", y)
 
# Swap code
x ^= y # x = 1111, y = 1010
y ^= x # y = 0101, x = 1111
x ^= y # x = 1010, y = 0101
 
print ("After swapping: ")
print("Value of x : ", x, " and y : ", y)

Output: 
 

Before swapping: 
Value of x :  5  and y :  10
After swapping: 
Value of x :  10  and y :  5


Method 3 :- Using Addition and Subtraction Operators 
 

x = x + y 
y = x - y
x = x - y


This method works for variables that have numeric values.
 

Python




# Python code to swap two numbers
# using + and - operators
 
 
x = 5.4
y = 10.3
 
print ("Before swapping: ")
print("Value of x : ", x, " and y : ", y)
 
# Swap code
x = x + y # x = 15.7, y = 10.3
y = x - y # x = 15.7, y = 5.4
x = x - y # x = 10.3, y = 5.4
 
print ("After swapping: ")
print("Value of x : ", x, " and y : ", y)

Output: 
 



Before swapping: 
Value of x :  5.4  and y :  10.3
After swapping: 
Value of x :  10.3  and y :  5.4


Method 4 :- Using Division and Multiplication Operators 
 

x = x * y
y = x / y
x = x / y


This method works for variables that have numeric values other than 0 .
 

Python




# Python code to swap two numbers
# using / and * operators
 
 
x = 5.4
y = 10.3
 
print ("Before swapping: ")
print("Value of x : ", x, " and y : ", y)
 
# Swap code
x = x * y # x = 55.62, y = 10.3
y = x / y # x = 55.62, y = 5.4
x = x / y # x = 10.3, y = 5.4
 
print ("After swapping: ")
print("Value of x : ", x, " and y : ", y)

Output: 
 

Before swapping: 
Value of x :  5.4  and y :  10.3
After swapping: 
Value of x :  10.3  and y :  5.4


Method 4: Using both bitwise operators and arithmetic operators:
 

Python3




# python program to swap two numbers
# using bitwise addition for swapping
 
 
   
x = 5;
y = 10;
   
print ("Before swapping: ") ;
print("Value of x : ", x, " and y : ", y) ;
   
# same as x = x + y
x = (x & y) + (x|y) ;
   
#vsame as y = x - y
y = x + (~y) + 1 ;
   
# same as x = x - y
x = x + (~y) + 1 ;
   
print ("After swapping: ")
print("Value of x : ", x, " and y : ", y)
 
# This code is contributed by bunnyram19

Output:

Before swapping: 
Value of x :  5  and y :  10
After swapping: 
Value of x :  10  and y :  5

 




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