Swap two numbers without using third variable. There are two common ways to swap two numbers without using third variable.

Solution 1: Using + and -

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

#include<stdio.h> int main() { int a=10, b=20; 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); return 0; }

Output:

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

Solution 2: Using * and /

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

#include<stdio.h> #include<stdlib.h> int main() { int a=10, b=20; 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) system("cls"); printf("\nAfter swap a=%d b=%d",a,b); return 0; }

Output:

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