C++ Program to Swap Two Numbers:Swapping means to interchange the value of two variables.For example if  variable a store 10 and another variable b store 20 then after swapping  b has 10 and a has 20. In C/C++ we can do the swapping in two way :- 
- using extra variable
 - without using extra variable
 
C++ Program to Swap Two Numbers using extra variable
#include <iostream>
using namespace std;
int main() {
    int a = 25, b = 15, temp;
    cout << "Before swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;
    temp = a;
    a = b;
    b = temp;
    cout << "\nAfter swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;
    return 0;
}
Output
Before swapping.a = 25, b = 15 
After swapping. a = 15, b = 25
C++ Program to Swap Two Numbers without using extra variable
#include <iostream>
using namespace std;
int main() {
    int a = 25, b = 15;
    cout << "Before swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;
    a = a + b;
    b = a - b;
    a = a - b;
    cout << "\nAfter swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;
    return 0;
}
Output
Before swapping.a = 25, b = 15 
After swapping. a = 15, b = 25
