C Program to swap two numbers without third variable

We can swap two numbers without using third variable. There are two common ways to swap two numbers without using third variable:

By + and -
By * and /

Program 1: Using + and -

Let's see a simple c example to swap two numbers without using third variable.

#include<stdio.h>
#include<conio.h>
main()
{
int a=10, b=20;  
clrscr();  
printf("Before swap a=%d b=%d",a,b);  

a=a+b;//a=30 (10+20)
b=a-b;//b=10 (30-20)
a=a-b;//a=20 (30-10)

printf("\nAfter swap a=%d b=%d",a,b);
getch();
}

Output:

Before swap a=10 b=20
After swap a=20 b=10

Program 2: Using * and /

Let's see another example to swap two numbers using * and /.

#include<stdio.h>
#include<conio.h>
main()
{
int a=10, b=20;  
clrscr();  
printf("Before swap a=%d b=%d",a,b);  

a=a*b;//a=200 (10*20)
b=a/b;//b=10 (200/20)
a=a/b;//a=20 (200/10)

printf("\nAfter swap a=%d b=%d",a,b); 
getch();
}

Output:

Before swap a=10 b=20
After swap a=20 b=10

Next TopicC Programs

← prev next →

C Programs

C Interview

C Program to swap two numbers without third variable

Program 1: Using + and -

Program 2: Using * and /