## Swapping without using a third variable in C++

This program will swap the value of these two numbers without using a temporary variable. The idea behind this concept is very simple. First we will sum the two given numbers and store it in a. Then subtract b from a and store it in b, Again subtract b from a and store it in a. That's all the numbers are swapped

## Source code :

```#include <iostream>

using namespace std;

int main(){

int a,b;

cout<<"Enter the value of a : ";
cin>>a;

cout<<"\nEnter the value of b : ";
cin>>b;

cout<<"\nThe first value is "<<a;
cout<<" and the second is "<<b<<endl;

a=a+b;
b=a-b;
a=a-b;

cout<<"===  After Swapping  ===\n";
cout<<"The first value is "<<a;
cout<<" and the second is "<<b<<endl;

return 0;

}

```

## Output :

```Enter the value of a : 10
Enter the value of b : 20
The first value is 10 and the second is 20
===  After Swapping  ===
The first value is 20 and the second is 10```

## Algorithm :

1. Declare two variables a,b and get the values from the user
2. Add `a` and `b` and assign it to `a` ie. `a=a+b`
3. Subtract `b` from `a` and assign it to `b` ie. `b=a-b`
4. Subtract `b` from `a` and assign it to `a` ie. `a=a-b`
5. Print the value of a and b