［C++］不使用中间变量交换两个数

http://pppboy.blog.163.com/blog/static/30203796201082563750874/

一、问题

有两个变量a，b，不使用任何中间变量交换它们。

二、解决方案

//-------------------------------- 
// 环境：VS2005 
// 用途：不用中间变量交换两个数 
// 时间：2010.9.25 
// 作者：http://pppboy.blog.163.com 
//-------------------------------- 
#include "stdafx.h" 
#include <iostream> 
using namespace std; 
//交换a，b 
void fSwap1(int& a, int& b) 
{ 
    a = a ^ b; 
    b = a ^ b; 
    a = a ^ b; 
} 
//交换a，b的另一种方法 
void fSwap2(int& a, int& b) 
{ 
    a = a + b; 
    b = a - b; 
    a = a - b; 
} 
//再一种方法 
void fSwap3(int& a, int& b) 
{ 
    a = a * b; 
    b = a / b; 
    a = a / b; 
} 
int main(int argc, char* argv[]) 
{ 
    int a, b; 
    cout << "------------------------------" << endl; 
    cout << "input a :" << endl; 
    cin >> a; 
    cout << "input b :" << endl; 
    cin >> b; 
    cout << "------------------------------" << endl; 
    cout << "a = " << a << endl; 
    cout << "b = " << b << endl; 
    cout << "------------------------------" << endl; 
    fSwap1(a, b); 
    cout << "after swap (1):" << endl; 
    cout << "a = " << a << endl; 
    cout << "b = " << b << endl; 
    fSwap2(a, b); 
    cout << "after swap (2):" << endl; 
    cout << "a = " << a << endl; 
    cout << "b = " << b << endl; 
    fSwap3(a, b); 
    cout << "after swap (3):" << endl; 
    cout << "a = " << a << endl; 
    cout << "b = " << b << endl; 
    system("pause"); 
    return 0; 
} 

结果为：

------------------------------ 
input a : 
32 
input b : 
65 
------------------------------ 
a = 32 
b = 65 
------------------------------ 
after swap (1): 
a = 65 
b = 32 
after swap (2): 
a = 32 
b = 65 
after swap (3): 
a = 65 
b = 32 
请按任意键继续. . .

当然，第一个还是最好，因为它不担心a，b数字大时越界的问题。