C Program to Swap two Numbers without using third variable

Write a c program to swap two numbers without using third variable. Given two input numbers, We have to write a code to swap two numbers without using third variable. In my previous post, I have explained a c program to swap two numbers using third variable. This question is generally asked in an interview.

Programming questions on linked list

Swap two numbers using Bitwise XOR Operator

Algorithm to swap two numbers without using third variable

Let’s say we have two numbers a and b. We need to swap these two numbers without using any temp or third variable.

Step 1 – Add the value of a and b then assign the sum to variable a.

Step 2 – Subtract the value of variable b from variable a and assign it to variable b.

Step 3 – Subtract the value of variable a and b and assign it to variable a.

Let’s take an example to understand this algorithm. Suppose the value of variable a is 3 and variable b is 4.

a = 3 and b =4

Output – a = 4 and b = 3.

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C Program to Swap Two Numbers without using Third Variable

C Program to Swap Two Numbers without using Third Variable

C Program to Swap Two Numbers without Using Third Variable

C Program to Swap Two Numbers using Multiplication and Division

In this example, We write a code to swap two numbers using multiplication and division. We won’t use any third or temporary variable to swap two numbers.

Explanation

Input :  a  = 5  and b = 10

a = a * b ( 5 * 10 = 50)

b = a / b (50 / 10 = 5)

a = a/b (50 / 5 = 10)

Output : a = 10 and b = 5

Stack program in c

Conclusion

I have written and explained c program to swap two numbers without using third variable. If you still face any difficulty you can let us know through your comments.

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