C++快速入门 第十二讲：传值、传址和传引用

实例1：值传递

 1 #include<iostream>
 2 
 3 void changeAge(int age,int newAge); 
 4 int main()
 5 {
 6     int age = 24;//定义一个age,占一处地址 
 7     std::cout << "My age is " << age <<"\n";
 8     
 9     changeAge(age,age + 1);
10     
11     std::cout << "Now my age is " << age << "\n";
12     
13     return 0;
14 }
15 
16 void changeAge(int age,int newAge)//再定义一个age,占另一处地址 
17 {
18     age = newAge;
19     std::cout << "In this, my age is " << age << "\n"; 
20 }

绕开“值传递”问题的第一种方法是向函数传递变量的地址取代他的值。

实例2：指针地址传递

 1 #include<iostream>
 2 
 3 void changeAge(int *age,int newAge); 
 4 int main()
 5 {
 6     int age = 24;//定义一个age,占一处地址 
 7     std::cout << "My age is " << age <<"\n";
 8     
 9     changeAge(&age,age + 1);
10     
11     std::cout << "Now my age is " << age << "\n";
12     
13     return 0;
14 }
15 
16 void changeAge(int *age,int newAge)//再定义一个age,占另一处地址 
17 {
18     *age = newAge;
19     std::cout << "In this, my age is " << *age << "\n"; 
20 }

实例3：两值互换

 1 #include<iostream>
 2 
 3 void swap(int *x,int *y);
 4 int main()
 5 {
 6     int x,y;
 7     
 8     std::cout << "请输入两个不同的值：";
 9     std::cin >> x >> y;
10     
11     swap(&x,&y);
12     
13     std::cout << "调换后输出：" << x << ' ' << y <<"\n\n"; 
14     
15 }
16 
17 void swap(int *x,int *y)
18 {
19     int temp;
20     temp = *x;
21     *x = *y;
22     *y = temp;
23 }

实例4：两值互换2

 1 #include<iostream>
 2 
 3 void swap(int *x,int *y);
 4 int main()
 5 {
 6     int x,y;
 7     
 8     std::cout << "请输入两个不同的值：";
 9     std::cin >> x >> y;
10     
11     swap(&x,&y);
12     
13     std::cout << "调换后输出：" << x << ' ' << y <<"\n\n"; 
14     
15 }
16 
17 void swap(int *x,int *y)
18 {
19     *x ^= *y;
20     *y = *x;
21     *x ^= *y;
22 }

实例5：不用指针的两值交换

 1 #include <iostream> 
 2 
 3 void swap(int &x,int &y);
 4 
 5 int main()
 6 {
 7     int x,y;
 8     std::cout << "请输入两个不同的值：";
 9     std::cin >> x >> y;
10     
11     swap(x,y);
12     std::cout << "调换后输出：" << x << ' ' << y << "\n\n";
13     
14     return 0;
15 }
16 
17 void swap(int &x,int &y)
18 {
19     int temp;
20     temp = x;
21     x = y;
22     y = temp;
23 }