关于两数异或交换的问题～～

void swap(int& a, int& b)
{
a=a^b;
b=a^b;
a=a^b;
}
为什么有时候当a == b，交换后两个都变成0了，比如a =6,b=6,经过函数处理后，都变成0了，单独测试是OK的，用在程序里就这样了

不可能的，你仔细看过了？


#include <iostream>
using namespace std;
void swap(int& a, int& b)
{
a=a^b;
b=a^b;
a=a^b;
}
void exchange(int &a, int &b)
{
a = a + b;
b = a - b;
a = a - b;
}
int main()
{
int a = 0, b = 0;
cout << "Input a and b:"<<endl;
cin >> a >> b;
swap(a, b);
cout << "SWQPED: a = " << a << ", b = " << b << endl;

cout << "Input a and b:"<<endl;
cin >> a >> b;
exchange(a, b);
cout << "EXCHANGED: a = " << a << ", b = " << b << endl;
return 0;
}

Outcome:


Input a and b:
3 3
SWQPED: a = 3, b = 3
Input a and b:
4 4
EXCHANGED: a = 4, b = 4