text: #include <iostream>
  using std::cout;
  using std::endl;
  
  void swap1(int num1, int num2) {
  	int tmp = num1;
  	num1 = num2;
  	num2 = tmp;
  }
  
  void swap2(int* num1, int* num2) {
  	int tmp = *num1;
  	*num1 = *num2;
  	*num2 = tmp;
  }
  
  void swap3(int& num1, int& num2) {
  	int tmp = num1;
  	num1 = num2;
  	num2 = tmp;
  }
  
  int main() {
  	int num1 = 1;
  	int num2 = 3;
  	int num3 = 1;
  	int num4 = 3;
  	cout << num1 << " " << num2 << endl;
  	swap1(num1, num2);
  	cout << "swap1 " << num1 << num2 << endl;
  	cout << num1 << " " << num2 << endl;
  	swap2(&num1, &num2);
  	cout << "swap2 " << num1 << num2 << endl;
  	cout << num3 << " " << num4 << endl;
  	swap3(num3, num4);
  	cout << "swap3 " << num3 << num4 << endl;
  
  	return 0;
  }