  # Swap Number

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

1. By + and –
2. By * and /

## Program 1: Using + and –

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

1. #include<stdio.h>
2. #include<conio.h>
3. main()
4. {
5. int a=10, b=20;
6. clrscr();
7. printf(“Before swap a=%d b=%d”,a,b);
8. a=a+b;//a=30 (10+20)
9. b=a-b;//b=10 (30-20)
10. a=a-b;//a=20 (30-10)
11. printf(“\nAfter swap a=%d b=%d”,a,b);
12. getch();
13. }

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 /.

1. #include<stdio.h>
2. #include<conio.h>
3. main()
4. {
5. int a=10, b=20;
6. clrscr();
7. printf(“Before swap a=%d b=%d”,a,b);
8. a=a*b;//a=200 (10*20)
9. b=a/b;//b=10 (200/20)
10. a=a/b;//a=20 (200/10)
11. printf(“\nAfter swap a=%d b=%d”,a,b);
12. getch();
13. }

Output:

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