交换两个实参的值（c++）

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1. 引用

#include <iostream>
using namespace std;
void swap( int &a, int &b )
{
    int temp;
    temp=a; a=b; b=temp;
}

int main()
{
    int x=3, y=5;
    cout<<" x= "<<x<<" y= "<<y<<endl;
    swap( x, y );
    cout<<" x= "<<x<<" y= "<<y<<endl;
    return 0;
}

2. 指针

#include <iostream>
using namespace std;
void swap( int *a, int *b )
{
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}

int main()
{
    int x=3, y=5;
    cout<<" x= "<<x<<" y= "<<y<<endl;
    swap( &x, &y );
    cout<<" x= "<<x<<" y= "<<y<<endl;
    return 0;
}

几个错误举例：

错误示例1：（光改变形参是没有用的）

#include <iostream>
using namespace std;
void swap( int a, int b )
{
    int temp;
    temp=a; a=b; b=temp;
}

int main()
{
    int x=3, y=5;
    cout<<" x= "<<x<<" y= "<<y<<endl;
    swap( x, y );
    cout<<" x= "<<x<<" y= "<<y<<endl;
    return 0;
}

错误示例2：（指针概念不清，不知道新定义的指针temp指向哪里）

#include <iostream>
using namespace std;
void swap( int *a, int *b )
{
    int *temp;
    *temp = *a;
    *a = *b;
    *b = *temp;
}

int main()
{
    int x=3, y=5;
    cout<<" x= "<<x<<" y= "<<y<<endl;
    swap( &x, &y );
    cout<<" x= "<<x<<" y= "<<y<<endl;
    return 0;
}

错误示例3：（指针概念不清，交换了地址）

#include <iostream>
using namespace std;
void swap( int *a, int *b )
{
    int *temp;
    temp = a;
    a = b;
    b = temp;
}

int main()
{
    int x=3, y=5;
    cout<<" x= "<<x<<" y= "<<y<<endl;
    swap( &x, &y );
    cout<<" x= "<<x<<" y= "<<y<<endl;
    return 0;
}