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.
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//Steps to swap two numbers without using third variable a = a + b b = a - b a = a - b; |
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
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a = a + b = 3 + 4 = 7 // 7 is assigned b = a - b = 7 - 4 = 3 // Now the value of b is 3 a = a - b = 7 - 3 = 4 |
Output – a = 4 and b = 3.
C Program to Swap Two Numbers without using Third Variable
C Program to Swap Two Numbers without Using Third Variable
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#include <stdio.h> int main() { /* Declare two variables. */ int a, b; /* Take user input. */ printf("Enter two numbers a and b "); scanf("%d%d",&a ,&b); printf("\n Before swapping a = %d and b =%d", a, b); /* Logic to swap two numbers. */ a = a + b; b = a - b; a = a - b; printf("\n After swapping a = %d b = %d",a ,b); return 0; } |
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.
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#include int main(void) { /* Declare two variables. */ int a, b; /* Take user input. */ printf("Enter two numbers a and b \n"); scanf("%d %d",&a ,&b); printf("\n Before swapping a = %d and b =%d", a, b); a = a * b; b = a / b; a = a / b; printf("\n After swapping a = %d and b =%d", a, b); return 0; } |
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
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.
