Python program to swap two numbers without using a temporary variable

Problem Definition:

In this program, we will learn how to swap two numbers without using a temporary variable.

Logic of the program:

First, read two numbers from the keyboard. Display the numbers before swapping. Then swap the numbers without using a temporary variable. Then display the swapped numbers.

Steps (Algorithm):

Step 1: Read two numbers from standard input (keyboard). Say number 1 and number 2.

Step 2: Print or display original numbers (number 1 and number 2) on standard output.

Step 3: In this step we do the actual swapping of number without using temporary variable.

Let, number 1 be the first variable with value 20 and number 2 be the second variable with value 30.

Number 1 = Number 1 + Number 2

#Number 1 is 20 + 30 = 50

Number 2 = Number 1 – Number 2

#Number 2 is 50 – 30 = 20

Number 1 = Number 1 – Number 2

#Number 1 is 50 – 20 = 30

First, we add the value of the first variable to a second variable and store in the first variable that is in number 1. Then we subtract the value of the second variable from the first variable and store result in the second variable. Finally, we again subtract the value of the second variable from the first variable and store the result in first variable.

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Step 4: Display the swapped numbers.

Sample Input to the program:

Number 1 = 20

Number 2 = 30

Expected Output:

Number 1 = 30

Number 2 = 20

Program to swap two numbers without using a temporary variable:

#Python program to swap numbers using temporary variable
num1 = int (input ("Enter the first number: "))
num2 = int (input ("Enter the second number: "))

#Print original number
print ("Before swapping")
print ("First number is : ", num1)
print ("First number is : ", num2)

#Swapping without using temporary variable
num1 = num1 + num2
num2 = num1 - num2
num1 = num1 - num2

#Print Swapped number
print ("After swapping")
print ("First number is : ", num1)
print ("First number is : ", num2)

Output:

Before Swapping
Enter the first number: 20
Enter the second number: 30

After Swapping
First number is: 30
Second number is: 20

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