#include<iostream>using namespace std;void swap(int &a, int &b);int main(){    int num1 = 10;    int num2 = 20;    cout<<num1<<" "<<num2<<endl;    swap(num1, num2);    cout<<num1<<" "<<num2<<endl;    return 0;}void swap(int &a, int &b){    int temp = a;    a = b;    b = temp;}