Write a C++ program to swap values of two variables without using third one (logic explained step by step)

Write a C++ program to swap values of two variables without using third one.
Is it possible to swap water of two glass without using third one ?

Steps

User side:

1: User asked to enter the value for first variable
2: User asked to enter the value for second variable

3: User displayed the values of variables before and after swapping.

Developer side

1: Declare variables that are going to be used in program.

2: Input the  value for first variable from user.

3: Input the  value for second variable from user.

4: Pass both the values by reference to function 'swap' and store returned value in the first variable (its not compulsory).

5: In the function add both the values and store the addition in the first variable.

6: Now subtract 'b'(second variable) from 'a' (it contains addition of both values) and store it into 'b'.

7: Now subtract 'b'(second variable) from 'a' (it contains addition of both values) and store it into 'a'.

8: Return the control to the main function .

9: Program end here.

Here is the code:

#include<iostream>

using namespace std;

int swap(int&, int&);

int main()

{

int n1 = 0, n2 = 0;

int& first = n1;

int& second = n2;

cout << "Enter First number= ";

cin >> n1;

cout << "Enter Second number= ";

cin >> n2;

cout << "First number is= " << first << endl;

cout << "Second number is= " << second << endl;

first = swap(first, second);

cout << "After swapping values are " << endl << "First number is= " << first << endl << "Second number is= " << second << endl;

system("pause");

return 0;

}

int swap(int& a, int& b)

{

a = a + b;

b = a - b;

a = a - b;

return a;

}