不用第三方参数，交换两个参数的值

#include <iostream>using namespace std;void Swap1(int &a, int &b) { a = a + b - (b = a); }int main(){int a = 4, b = 5;cout << "before swap: ";cout << "a = " << a << ", b = " << b << endl;Swap1(a, b);cout << "after swap: ";cout << "a = " << a << ", b = " << b << endl;return 0;}

gcc 4.1.2运行，三个自定义函数都能交换两个变量的值。

VS 2008下面，Swap1()函数被优化了，没有正确交换两个变量的值，表示不懂。求解释~