C++ Program:

Example:

#include <iostream>
using namespace std;

int main() {
  int n1,n2;
  cout<<"Enter 1st number: ";
  cin>>n1;
  cout<<"Enter 2nd number: ";
  cin>>n2;
  n1=n1+n2;
  n2=n1-n2;
  n1=n1-n2;
  cout<<"After Swap"<<endl;
  cout<<"1st number :"<<n1<<"\n2nd number :"<<n2;
  return 0;
}

Output:

  Enter 1st number : 7
  Enter 2nd number : 15
  After Swap
  1st number : 15
  2nd number : 7

Here we are adding both values into one then used some maths

//Lets take n1=7, n2=3;

n1=n1+n2; //n1=7+3=10
n2=n1-n2; //n2=10-3=7
n1=n1-n2; //n1=10-7=3

//Finally you swaped & get n1=3, n2=7;